Chemistry Midterm Review Presentation! Aligned to the New York State Standards and Core Curriculum for The Physical SettingChemistry Can be used in any high-school chemistry class! Outline for Review 1) The Atom (Nuclear, Electron Config) 2) Matter (Phases, Types, Changes) 3) Bonding (Periodic Table, Ionic, Covalent) 4) Compounds (Formulas, Reactions, IMAFs) 5) Math of Chemistry (Formula Mass, Gas Laws,
Neutralization, etc.) The Atom 1) Nucleons 2) Isotopes 6) Electron Configuation 7) Development of the Atomic Model Nucleons Protons: +1 each, determines identity of element, mass of 1 amu, determined using atomic number, nuclear charge Neutrons: no charge, determines identity of isotope of an
element, 1 amu, determined using mass number - atomic number (amu = atomic mass unit) 3216S and 3316S are both isotopes of S S-32 has 16 protons and 16 neutrons S-33 has 16 protons and 17 neutrons All atoms of S have a nuclear charge of +16 due to the 16 protons. (c) 2006, Mark Rosengarten Isotopes Atoms of the same element MUST contain the same
number of protons. Atoms of the same element can vary in their numbers of neutrons, therefore many different atomic masses can exist for any one element. These are called isotopes. The atomic mass on the Periodic Table is the weight-average atomic mass, taking into account the different isotope masses and their relative abundance. Rounding off the atomic mass on the Periodic Table will tell you what the most common isotope of that element is. Weight-Average Atomic Mass
WAM = ((% A of A/100) X Mass of A) + ((% A of B/100) X Mass of B) + What is the WAM of an element if its isotope masses and abundances are: X-200: Mass = 200.0 amu, % abundance = 20.0 % X-204: Mass = 204.0 amu, % abundance = 80.0% amu = atomic mass unit (1.66 10-27 kilograms/amu) Most Common Isotope The weight-average atomic mass of Zinc is 65.39 amu. What is the most common isotope
of Zinc? Zn-65! What are the most common isotopes of: Co S Ag Pb FACT: one atomic mass unit (1.66 10-27 kilograms) is defined as 1/12 of the mass of an atom of C-12.
This method doesnt always work, but it (c) 2006, Use Mark Rosengarten usually does. it for the Regents exam. Electron Configuration Basic Configuration Valence Electrons Electron-Dot (Lewis Dot) Diagrams Excited vs. Ground State What is Light?
(c) 2006, Mark Rosengarten Basic Configuration The number of electrons is determined from the atomic number. Look up the basic configuration below the atomic number on the periodic table. (PEL: principal energy level = shell) He: 2 (2 e- in the 1st PEL) Na: 2-8-1 (2 e- in the 1st PEL, 8 in the 2nd and 1 in the 3rd) Br: 2-8-18-7 (2 e- in the 1st PEL, 8 in the 2nd, 18 in the 3rd and 7 in the 4th)
(c) 2006, Mark Rosengarten Valence Electrons The valence electrons are responsible for all chemical bonding. The valence electrons are the electrons in the outermost PEL (shell). He: 2 (2 valence electrons)
Na: 2-8-1 (1 valence electron) Br: 2-8-18-7 (7 valence electrons) The maximum number of valence electrons an atom can have is EIGHT, called a STABLE OCTET. (c) 2006, Mark Rosengarten Electron-Dot Diagrams The number of dots equals the number of valence electrons. The number of unpaired valence electrons in a nonmetal tells you how many covalent bonds that atom can form with
other nonmetals or how many electrons it wants to gain from metals to form an ion. The number of valence electrons in a metal tells you how many electrons the metal will lose to nonmetals to form an ion. Caution: May not work with transition metals. EXAMPLE DOT DIAGRAMS (c) 2006, Mark Rosengarten Example Dot Diagrams Carbon can also have this dot diagram, which it has when it forms
compounds. (c) 2006,organic Mark Rosengarten Excited vs. Ground State Configurations on the Periodic Table are ground state configurations. If electrons are given energy, they rise to higher energy levels (excited state). If the total number of electrons matches in the configuration, but the configuration doesnt match, the atom is in the excited state.
Na (ground, on table): 2-8-1 Example of excited states: 2-7-2, 2-8-0-1, 2-6-3 (c) 2006, Mark Rosengarten What Is Light? Light is formed when electrons drop from the excited state to the ground state. The lines on a bright-line spectrum come from specific energy level drops and are unique to each element. EXAMPLE SPECTRUM (c) 2006, Mark Rosengarten
EXAMPLE SPECTRUM This is the bright-line spectrum of hydrogen. The top numbers represent the PEL (shell) change that produces the light with that color and the bottom number is the wavelength of the light (in nanometers, or 10-9 m). No other element has the same bright-line spectrum as hydrogen, so these spectra can be used to identify elements or mixtures of elements. (c) 2006, Mark Rosengarten Development of the Atomic
Model Thompson Model Rutherford Gold Foil Experiment and Mode l Bohr Model Quantum-Mechanical Model (c) 2006, Mark Rosengarten Thompson Model The atom is a positively charged diffuse
mass with negatively charged electrons stuck in it. (c) 2006, Mark Rosengarten Rutherford Model The atom is made of a small, dense, positively charged nucleus with electrons at a distance, the vast majority of the volume of the atom is empty space. (c) 2006, Mark Rosengarten
Alpha particles shot at a thin sheet of gold foil: most go through (empty space). Some deflect or bounce off (small + charged nucleus). Bohr Model Electrons orbit around the nucleus in energy levels (shells). Atomic bright-line spectra was the clue.
(c) 2006, Mark Rosengarten Quantum-Mechanical Model Electron energy levels are wave functions. Electrons are found in orbitals, regions of space where an electron is most likely to be found. You cant know both where the electron is and where it is going at the same time. Electrons buzz around the nucleus like gnats buzzing around your head. (c) 2006, Mark Rosengarten
Properties of Phases Solids: Crystal lattice (regular geometric pattern), vibration motion only Liquids: particles flow past each other but are still attracted to each other. Gases: particles are small and far apart, they travel in a straight line until they hit something, they bounce off without losing any energy, they are so far apart from each other that they have effectively no attractive forces and their speed is directly proportional to the Kelvin temperature (Kinetic-Molecular Theory, Ideal Gas Theory)
(c) 2006, Mark Rosengarten Solids The positive and negative ions alternate in the ionic crystal lattice of NaCl. (c) 2006, Mark Rosengarten Liquids
When heated, the ions move faster and eventually separate from each other to form a liquid. The ions are loosely held together by the oppositely charged ions, but the ions are moving too fast for the crystal lattice to stay together. (c) 2006, Mark Rosengarten Gases Since all gas molecules spread out
the same way, equal volumes of gas under equal conditions of temperature and pressure will contain equal numbers of molecules of gas. 22.4 L of any gas at STP (1.00 atm and 273K) will contain one mole (6.02 X 1023) gas molecules. Since there is space between gas molecules, gases are affected by (c) 2006, Mark Rosengarten changes
in pressure. Types of Matter Substances (Homogeneous) Elements (cannot be decomposed by chemical change): Al, Ne, O, Br, H Compounds (can be decomposed by chemical change): NaCl, Cu(ClO3)2, KBr, H2O, C2H6 Mixtures Homogeneous: Solutions (solvent + solute) Heterogeneous: soil, Italian dressing, etc. (c) 2006, Mark Rosengarten
Elements A sample of lead atoms (Pb). All atoms in the sample consist of lead, so the substance is homogeneous. A sample of chlorine atoms (Cl). All atoms in the sample consist of chlorine, so the substance is homogeneous. (c) 2006, Mark Rosengarten
Compounds Lead has two charges listed, +2 and +4. This is a sample of lead (II) chloride (PbCl2). Two or more elements bonded in a wholenumber ratio is a COMPOUND. This compound is formed from the +4 version of lead. This is lead (IV) chloride (PbCl4). Notice how both samples of lead compounds have consistent composition throughout?
Compounds are homogeneous! (c) 2006, Mark Rosengarten Mixtures A mixture of lead atoms and chlorine atoms. They exist in no particular ratio and are not chemically combined with each other. They can be separated by physical means. A mixture of PbCl2 and PbCl4
formula units. Again, they are in no particular ratio to each other and can be separated without chemical change. (c) 2006, Mark Rosengarten Bonding 1) The Periodic Table 2) Ions 3) Ionic Bonding 4) Covalent Bonding
5) Metallic Bonding (c) 2006, Mark Rosengarten The Periodic Table Metals Nonmetals Metalloids Chemistry of Groups Electronegativity Ionization Energy (c) 2006, Mark Rosengarten
Metals Have luster, are malleable and ductile, good conductors of heat and electricity Lose electrons to nonmetal atoms to form positivel y charged ions in ionic bonds Large atomic radii compared to nonmetal atoms
Low electronegativity and ionization energy Left side of the periodic table (except H) (c) 2006, Mark Rosengarten Nonmetals Are dull and brittle, poor conductors Gain electrons from metal atoms to form negatively c
harged ions in ionic bonds Share unpaired valence electrons with other nonmetal atoms to form covalent bonds and molecules Small atomic radii compared to metal atoms High electronegativity and ionization energy Right side of the periodic table (except Group 18) (c) 2006, Mark Rosengarten Metalloids Found lying on the jagged line between metals and nonmetals flatly touching the line (except Al and Po).
Share properties of metals and nonmetals (Si is shiny like a metal, brittle like a nonmetal and is a semiconductor). (c) 2006, Mark Rosengarten Chemistry of Groups Group 1: Alkali Metals Group 2: Alkaline Earth Metals Groups 3-11: Transition Elements Group 17: Halogens Group 18: Noble Gases Diatomic Molecules (c) 2006, Mark Rosengarten
Group 1: Alkali Metals Most active metals, only found in compounds in nature React violently with water to form hydrogen gas and a strong base: 2 Na (s) + H2O (l) 2 NaOH (aq) + H2 (g) 1 valence electron Form +1 ion by losing that valence electron Form oxides like Na2O, Li2O, K2O (c) 2006, Mark Rosengarten
Group 2: Alkaline Earth Metals Very active metals, only found in compounds in nature React strongly with water to form hydrogen gas and a base: Ca (s) + 2 H2O (l) Ca(OH)2 (aq) + H2 (g) 2 valence electrons Form +2 ion by losing those valence electrons Form oxides like CaO, MgO, BaO (c) 2006, Mark Rosengarten
Groups 3-11: Transition Metals Many can form different possible charges of ions If there is more than one ion listed, give the charge as a Roman numeral after the name Cu+1 = copper (I) Cu+2 = copper (II) Compounds containing these metals can be colored. (c) 2006, Mark Rosengarten Group 17: Halogens Most reactive nonmetals
React violently with metal atoms to form halide compounds: 2 Na + Cl2 2 NaCl Only found in compounds in nature Have 7 valence electrons Gain 1 valence electron from a metal to form -1 ions Share 1 valence electron with another nonmetal atom to form one covalent bond. (c) 2006, Mark Rosengarten Group 18: Noble Gases
Are completely nonreactive since they have eight valence electrons, making a stable octet. Kr and Xe can be forced, in the laboratory, to give up some valence electrons to react with fluorine. Since noble gases do not naturally bond to any other elements, one atom of noble gas is considered to be a molecule of noble gas. This is called a monatomic molecule. Ne represents an atom of Ne and a molecule of Ne. (c) 2006, Mark Rosengarten
Diatomic Molecules Br, I, N, Cl, H, O and F are so reactive that they exist in a more chemically stable state when they covalently bond with another atom of their own element to make two-atom, or diatomic molecules. Br2, I2, N2, Cl2, H2, O2 and F2 The decomposition of water: 2 H2O 2 H2 + O2 (c) 2006, Mark Rosengarten Electronegativity An atoms attraction to electrons in a chemical bond.
F has the highest, at 4.0 Fr has the lowest, at 0.7 If two atoms that are different in EN (END) from each other by 1.7 or more collide and bond (like a metal atom and a nonmetal atom), the one with the higher electronegativity will pull the valence electrons away from the atom with the lower electronegativity to form a (-) ion. The atom that was stripped of its valence electrons forms a (+) ion. If the two atoms have an END of less than 1.7, they will share their unpaired valence electronscovalent bond! (c) 2006, Mark Rosengarten
Ionization Energy The energy required to remove the most loosely held valence electron from an atom in the gas phase. High electronegativity means high ionization energy because if an atom is more attracted to electrons, it will take more energy to remove those electrons. Metals have low ionization energy. They lose electrons easily to form (+) charged ions. Nonmetals have high ionization energy but high electronegativity. They gain electrons easily to form (-) charged ions when reacted with metals, or share unpaired valence electrons with other nonmetal atoms.
(c) 2006, Mark Rosengarten Ions Ions are charged particles formed by the gain or loss of electrons. Metals lose electrons (oxidation) to form (+) charged cations. Nonmetals gain electrons (reduction) to form (-) charged anions. Atoms will gain or lose electrons in such a way that they end up with 8 valence electrons (stable octet). The exceptions to this are H, Li, Be and B, which are not
large enough to support 8 valence electrons. They must be satisfied with 2 (Li, Be, B) or 0 (H). (c) 2006, Mark Rosengarten Metal Ions (Cations) Na: 2-8-1 Na+1: 2-8 Ca: 2-8-8-2 Ca+2: 2-8-8 Al: 2-8-3 Al+3: 2-8 Note that when the atom
loses its valence electron, the next lower PEL becomes the valence PEL. Notice how the dot diagrams for metal ions lack dots! Place brackets around the element symbol and put the charge on the upper right outside! (c) 2006, Mark Rosengarten
Nonmetal Ions (Anions) F: 2-7 F-1: 2-8 O: 2-6 O-2: 2-8 Note how the ions all have 8 valence electrons. Also note the gained electrons as red dots. Nonmetal ion dot diagrams show 8 dots, with brackets around the dot diagram and the charge of the ion written to the upper right
side outside the brackets. N: 2-5 N-3: 2-8 (c) 2006, Mark Rosengarten Ionic Bonding If two atoms that are different in EN (END) from each other by 1.7 or more collide and bond (like a metal atom and a nonmetal atom), the one with the higher electronegativity will pull the valence electrons away from the atom with the lower electronegativity to form a (-) ion. The atom that was
stripped of its valence electrons forms a (+) ion. The oppositely charged ions attract to form the bond. It is a surface bond that can be broken by melting or dissolving in water. Ionic bonding forms ionic crystal lattices, not molecules. (c) 2006, Mark Rosengarten Example of Ionic Bonding (c) 2006, Mark Rosengarten Covalent Bonding If two nonmetal atoms have an END of 1.7 or less, they
will share their unpaired valence electrons to form a covalent bond. A particle made of covalently bonded nonmetal atoms is called a molecule. If the END is between 0 and 0.4, the sharing of electrons is equal, so there are no charged ends. This is NONPOLAR covalent bonding. If the END is between 0.5 and 1.7, the sharing of electrons is unequal. The atom with the higher EN will be - and the one with the lower EN will be + charged. This is a (c) 2006, Mark Rosengarten POLAR covalent bonding.
(means partial) Examples of Covalent Bonding (c) 2006, Mark Rosengarten Metallic Bonding Metal atoms of the same element bond with each other by sharing valence electrons that they lose to each other. This is a lot like an atomic game of hot potato, where metal kernals (the atom inside the valence electrons) sit in a crystal lattice, passing valence electrons back and forth
between each other). Since electrons can be forced to travel in a certain direction within the metal, metals are very good at conducting electricity in all phases. (c) 2006, Mark Rosengarten Compounds 1) Types of Compounds 2) Formula Writing 3) Formula Naming 4) Empirical Formulas 5) Molecular Formulas
6) Types of Chemical Reactions 7) Balancing Chemical Reactions 8) Attractive Forces (c) 2006, Mark Rosengarten Types of Compounds Ionic: made of metal and nonmetal ions. Form an ionic crystal lattice when in the solid phase. Ions separate when melted or dissolved in water, allowing electrical conduction. Examples: NaCl, K2O, CaBr2 Molecular: made of nonmetal atoms bonded to form a
distinct particle called a molecule. Bonds do not break upon melting or dissolving, so molecular substances do not conduct electricity. EXCEPTION: Acids [H+A- (aq)] ionize in water to form H3O+ and A-, so they do conduct. Network: made up of nonmetal atoms bonded in a seemingly endless matrix of covalent bonds with no (c) 2006, Mark Rosengarten distinguishable molecules. Very high m.p., dont conduct.
Ionic Compounds Ionic Crystal Structure, then adding heat (or dissolving in water) to break up the crystal into a liquid composed of free-moving ions. (c) 2006, Mark Rosengarten Molecular Compounds (c) 2006, Mark Rosengarten Network Solids Network solids are made of nonmetal atoms covalently bonded together to form large crystal lattices. No individual
molecules can be distinguished. Examples include C (diamond) and SiO2 (quartz). Corundum (Al2O3) also forms these, even though Al is considered a metal. Network solids are among the hardest materials known. They have extremely high melting points and do not conduct electricity. (c) 2006, Mark Rosengarten Formula Writing The charge of the (+) ion and the charge of the (-) ion must cancel out to make the formula. Use subscripts to indicate how many atoms of each element there are in the
compound, no subscript if there is only one atom of that element. Na+1 and Cl-1 = NaCl Ca+2 and Br-1 = CaBr2 Al+3 and O-2 = Al2O3 Zn+2 and PO4-3 = Zn3(PO4)2 Try these problems! (c) 2006, Mark Rosengarten Formulas to Write Ba+2 and N-3 NH4+1 and SO4-2 Li+1 and S-2
Cu+2 and NO3-1 Al+3 and CO3-2 Fe+3 and Cl-1 Pb+4 and O-2 Pb+2 and O-2 (c) 2006, Mark Rosengarten Formula Naming Compounds are named from the elements or polyatomic ions that form them. KCl = potassium chloride Na2SO4 = sodium sulfate
(NH4)2S = ammonium sulfide AgNO3 = silver nitrate Notice all the metals listed here only have one charge listed? So what do you do if a metal has more than one charge listed? Take a peek! (c) 2006, Mark Rosengarten The Stock System CrCl2 = chromium (II) chloride Try
CrCl3 = chromium (III) chloride Co(NO3)2 and CrCl6 = chromium (VI) chloride Co(NO3)3 FeO = iron (II) oxide Fe2O3 = iron (III) oxide MnS = manganese (II) sulfide
MnS2 = manganese (IV) sulfide The Roman numeral(c)is2006, Rosengarten theMark charge of the metal ion! Empirical Formulas Ionic formulas: represent the simplest whole number mole ratio of elements in a compound. Ca3N2 means a 3:2 ratio of Ca ions to N ions in the
compound. Many molecular formulas can be simplified to empirical formulas Ethane (C2H6) can be simplified to CH3. This is the empirical formulathe ratio of C to H in the molecule. All ionic compounds have empirical formulas. (c) 2006, Mark Rosengarten Molecular Formulas The count of the actual number of atoms of each element in a molecule. H2O: a molecule made of two H atoms and one O atom
covalently bonded together. C2H6O: A molecule made of two C atoms, six H atoms and one O atom covalently bonded together. Molecular formulas are whole-number multiples of empirical formulas: H2O = 1 X (H2O) C8H16 = 8 X (CH2) Calculating Molecular (c) 2006, Mark Rosengarten Formulas Types of Chemical Reactions
Redox Reactions: driven by the loss (oxidation) and gain (reduction) of electrons. Any species that does not change charge is called the spectator ion. Synthesis Decomposition Single Replacement Ion Exchange Reaction: driven by the formation of an insoluble precipitate. The ions that remain dissolved throughout are the spectator ions. Double Replacement (c) 2006, Mark Rosengarten
Synthesis Two elements combine to form a compound 2 Na + O2 Na2O Same reaction, with charges added in: 2 Na0 + O20 Na2+1O-2 Na0 is oxidized (loses electrons), is the reducing agent O20 is reduced (gains electrons), is the oxidizing agent Electrons are transferred from the Na0 to the O20. No spectator ions, there are only two elements here. (c) 2006, Mark Rosengarten
Decomposition A compound breaks down into its original elements. Na2O 2 Na + O2 Same reaction, with charges added in: Na2+1O-2 2 Na0 + O20 O-2 is oxidized (loses electrons), is the reducing agent Na+1 is reduced (gains electrons), is the oxidizing agent Electrons are transferred from the O-2 to the Na+1. No spectator ions, there are only two elements here. (c) 2006, Mark Rosengarten Single Replacement
An element replaces the same type of element in a compound. Ca + 2 KCl CaCl2 + 2 K Same reaction, with charges added in: Ca0 + 2 K+1Cl-1 Ca+2Cl2-1 + 2 K0 Ca0 is oxidized (loses electrons), is the reducing agent K+1 is reduced (gains electrons), is the oxidizing agent Electrons are transferred from the Ca 0 to the K+1. Cl-1 is the spectator ion, since its charge doesnt change. (c) 2006, Mark Rosengarten Double Replacement The (+) ion of one compound bonds to the (-) ion of another
compound to make an insoluble precipitate. The compounds must both be dissolved in water to break the ionic bonds first. NaCl (aq) + AgNO3 (aq) NaNO3 (aq) + AgCl (s) The Cl-1 and Ag+1 come together to make the insoluble precipitate, which looks like snow in the test tube. No species change charge, so this is not a redox reaction. Since the Na+1 and NO3-1 ions remain dissolved throughout the reaction, they are the spectator ions. How do identify the precipitate? (c) 2006, Mark Rosengarten
Identifying the Precipitate The precipitate is the compound that is insoluble. AgCl is a precipitate because Cl- is a halide. Halides are soluble, (c) 2006, Mark Rosengarten except when combined with Ag+ and others. Balancing Chemical Reactions Balance one element or ion at a time Use a pencil Use coefficients only, never change formulas
Revise if necessary The coefficient multiplies everything in the formula by that amount 2 Ca(NO3)2 means that you have 2 Ca, 4 N and 12 O. Examples for you to try! (c) 2006, Mark Rosengarten Reactions to Balance ___NaCl ___Na + ___Cl2 ___Al + ___O2 ___Al2O3 ___SO3 ___SO2 + ___O2 ___Ca + ___HNO3 ___Ca(NO3)2 + ___H2
__FeCl3 + __Pb(NO3)2 __Fe(NO3)3 + __PbCl2 (c) 2006, Mark Rosengarten Attractive Forces Molecules have partially charged ends. The + end of one molecule attracts to the - end of another molecule. Ions are charged (+) or (-). Positively charged ions attract other to form ionic bonds, a type of attractive force. Since partially charged ends result in weaker attractions than fully charged ends, ionic compounds generally have much higher melting points than molecular compounds.
Determining Polarity of Molecules Hydrogen Bond Attractions (c) 2006, Mark Rosengarten Determining Polarity of Molecules ----------------------------------------------------------------------------- (c) 2006, Mark Rosengarten Hydrogen Bond Attractions
A hydrogen bond attraction is a very strong attractive force between the H end of one polar molecule and the N, O or F end of another polar molecule. This attraction is so strong that water is a liquid at a temperature where most compounds that are much heavier than water (like propane, C3H8) are gases. This also gives water its surface tension and its ability to form a (c) 2006, Mark Rosengarten
meniscus in a narrow glass tube. Math of Chemistry 1) Formula Mass 2) Percent Composition 3) Mole Problems 4) Gas Laws 5) Neutralization 6) Concentration 7) Significant Figures and Rounding 8) Metric Conversions 9) Calorimetry (c) 2006, Mark Rosengarten
Formula Mass Gram Formula Mass = sum of atomic masses of all elements in the compound Round given atomic masses to the nearest tenth H2O: (2 X 1.0) + (1 X 16.0) = 18.0 grams/mole Na2SO4: (2 X 23.0)+(1 X 32.1)+(4 X 16.0) = 142.1 g/mole Now you try: BaBr2 CaSO4 Al2(CO3)3
(c) 2006, Mark Rosengarten Percent Composition What is the % composition, by mass, of each element in SiO2? %Si = (28.1/60.1) X 100 = 46.8% %O = (2 X 16.0 = 32.0), (32.0/60.1) X 100 = 53.2% The mass of part is the number of atoms of that element in the compound. The mass of whole is the formula mass of the compound. Dont forget to take atomic mass to the nearest tenth! This is a problem
for Mark youRosengarten to try. (c) 2006, Practice Percent Composition Problem What is the percent by mass of each element in Li2SO4? (c) 2006, Mark Rosengarten Mole Problems Grams <=> Moles
Molecular Formula Stoichiometry (c) 2006, Mark Rosengarten Grams <=> Moles How many grams will 3.00 moles of NaOH (40.0 g/mol) weigh? 3.00 moles X 40.0 g/mol = 120. g How many moles of NaOH (40.0 g/mol) are represented by 10.0 grams?
(10.0 g) / (40.0 g/mol) = 0.250 mol (c) 2006, Mark Rosengarten Molecular Formula Molecular Formula = (Molecular Mass/Empirical Mass) X Empirical Formula What is the molecular formula of a compound with an empirical formula of CH2 and a molecular mass of 70.0 grams/mole? 1) Find the Empirical Formula Mass: CH2 = 14.0
2) Divide the MM/EM: 70.0/14.0 = 5 3) Multiply the molecular formula by the result: 5 (CH2) = C5H10 (c) 2006, Mark Rosengarten Stoichiometry Moles of Target = Moles of Given X (Coefficent of Target/Coefficient of given) Given the balanced equation N2 + 3 H2 2 NH3, How
many moles of H2 need to be completely reacted with N2 to yield 20.0 moles of NH3? 20.0 moles NH3 X (3 H2 / 2 NH3) = 30.0 moles H2 (c) 2006, Mark Rosengarten Gas Laws Make a data table to put the numbers so you can eliminate the
words. Make sure that any Celsius temperatures are converted to Kelvin (add 273). Rearrange the equation before substituting in numbers. If you are trying to solve for T2, get it out of the denominator first by crossmultiplying. If one of the variables is constant, then eliminate it. Try these problems! (c) 2006, Mark Rosengarten Gas Law Problem 1 A 2.00 L sample of N2 gas at
STP is compressed to 4.00 atm at constant temp-erature. What is the new volume of the gas? V2 = P1V1 / P2 = (1.00 atm)(2.00 L) / (4.00 atm) = 0.500 L (c) 2006, Mark Rosengarten Gas Law Problem 2 To what temperature must a 3.000 L sample of O2 gas at
300.0 K be heated to raise the volume to 10.00 L? T2 = V2T1/V1 = (10.00 L)(300.0 K) / (3.000 L) = 1000. K (c) 2006, Mark Rosengarten Gas Law Problem 3 A 3.00 L sample of NH3 gas at 100.0 kPa is cooled from 500.0 K to 300.0 K and its pressure is reduced to 80.0 kPa. What is the new volume of the gas? V2 = P1V1T2 / P2T1
= (100.0 kPa)(3.00 L)(300. K) / (80.0 kPa)(500. K) = 2.25 L (c) 2006, Mark Rosengarten Neutralization 10.0 mL of 0.20 M HCl is neutralized by 40.0 mL of NaOH. What is the concentration of the NaOH? #H MaVa = #OH MbVb, so Mb = #H MaVa / #OH Vb
= (1)(0.20 M)(10.0 mL) / (1) (40.0 mL) = 0.050 M How many mL of 2.00 M H2SO4 are needed to completely neutralize 30.0 mL of 0.500 M KOH? (c) 2006, Mark Rosengarten Concentration Molarity Parts per Million Percent by Mass Percent by Volume (c) 2006, Mark Rosengarten
Molarity What is the molarity of a 500.0 mL solution of NaOH (FM = 40.0) with 60.0 g of NaOH (aq)? Convert g to moles and mL to L first! M = moles / L = 1.50 moles / 0.5000 L = 3.00 M How many grams of NaOH does it take to make 2.0 L of a 0.100 M solution of NaOH (aq)? Moles = M X L = 0.100 M X 2.0 L = 0.200 moles
Convert moles to grams: 0.200 moles X 40.0 g/mol = 8.00 g (c) 2006, Mark Rosengarten Parts Per Million 100.0 grams of water is evaporated and analyzed for lead. 0.00010 grams of lead ions are found. What is the concentration of the lead, in parts per million? ppm = (0.00010 g) / (100.0 g) X 1 000 000 = 1.0 ppm If the legal limit for lead in the water is 3.0 ppm, then the water sample is within the legal limits (its OK!)
(c) 2006, Mark Rosengarten Percent by Mass A 50.0 gram sample of a solution is evaporated and found to contain 0.100 grams of sodium chloride. What is the percent by mass of sodium chloride in the solution? % Comp = (0.100 g) / (50.0 g) X 100 = 0.200% (c) 2006, Mark Rosengarten Percent By Volume Substitute volume for mass in the above equation.
What is the percent by volume of hexane if 20.0 mL of hexane are dissolved in benzene to a total volume of 80.0 mL? % Comp = (20.0 mL) / (80.0 mL) X100 = 25.0% (c) 2006, Mark Rosengarten Sig Figs and Rounding How many Significant Figures does a number have? What is the precision of my measurement? How do I round off answers to addition and subtraction pr
oblems? How do I round off answers to multiplication and division problems? (c) 2006, Mark Rosengarten How many Sig Figs? Start counting sig figs at the first non-zero. All digits except place-holding zeroes are sig figs. Measurement
# of Sig Figs Measurement # of Sig Figs 0.115 cm 3 234 cm
3 0.00034 cm 2 67000 cm 2 0.00304 cm 3
_ 45000 cm 4 0.0560 cm 3 560. cm 3
0.00070700 cm 5 560.00 cm 5 (c) 2006, Mark Rosengarten What Precision? A numbers precision is determined by the furthest
(smallest) place the number is recorded to. 6000 mL : thousands place 6000. mL : ones place 6000.0 mL : tenths place 5.30 mL : hundredths place 8.7 mL : tenths place 23.740 mL : thousandths place (c) 2006, Mark Rosengarten Rounding with addition and subtraction Answers are rounded to the least precise place.
1) 4.732 cm 16.8 cm + 0.781 cm ---------22.313 cm 22.3 cm 2) 17.440 mL 3.895 mL + 16.77 mL
-------------38.105 mL 38.11 mL (c) 2006, Mark Rosengarten 3) 32.0 MW + 0.0059 MW --------------32.0059 MW 32.0 MW
Rounding with multiplication and division Answers are rounded to the fewest number of significant figures. 1) 37.66 KW x 2.2 h ---------82.852 KWh 83 KW h 2)
14.922 cm x 2.0 cm ----------2 29.844 cm 2 30. cm (c) 2006, Mark Rosengarten 3) 98.11 kg x 200 m ---------19 622 kgm
20 000 kg m Metric Conversions Determine how many powers of ten difference there are between the two units (no prefix = 100) and create a conversion factor. Multiply or divide the given by the conversion factor. How many kg are in 38.2 cg? (38.2 cg) /(100000 cg/kg) = 0.000382 km
How many mL in 0.988 dL? (0.988 dg) X (100 mL/dL) = 98.8 mL (c) 2006, Mark Rosengarten Calorimetry This equation can be used to determine any of the variables here. You will not have to solve for C, since we will always assume that the energy transfer is being absorbed by or released by a measured quantity of water, whose specific heat is given above. Solving for q
Solving for m Solving for DT (c) 2006, Mark Rosengarten Solving for q How many joules are absorbed by 100.0 grams of water in a calorimeter if the temperature of the water increases from 20.0oC to 50.0oC? q = mCDT = (100.0 g)(4.18 J/goC)(30.0oC) = 12500 J (c) 2006, Mark Rosengarten
Solving for m A sample of water in a calorimeter cup increases from 25oC to 50.oC by the addition of 500.0 joules of energy. What is the mass of water in the calorimeter cup? q = mCDT, so m = q / CDT = (500.0 J) / (4.18 J/goC)(25oC) = 4.8 g (c) 2006, Mark Rosengarten Solving for DT If a 50.0 gram sample of water in a calorimeter cup absorbs 1000.0 joules of energy, how much will the
temperature rise by? q = mCDT, so DT = q / mC = (1000.0 J)/(50.0 g)(4.18 J/g oC) = 4.8oC If the water started at 20.0oC, what will the final temperature be? Since the water ABSORBS the energy, its temperature will INCREASE by the DT: 20.0oC + 4.8oC = 24.8oC (c) 2006, Mark Rosengarten Kinetics and Thermodynamics 1) Reaction Rate
2) Heat of Reaction 3) Potential Energy Diagrams 4) Equilibrium 5) Le Chteliers Principle 6) Solubility Curves (c) 2006, Mark Rosengarten Reaction Rate Reactions happen when reacting particles collide with sufficient energy (activation energy) and at the proper angle. Anything that makes more collisions in a given time will
make the reaction rate increase. Increasing temperature Increasing concentration (pressure for gases) Increasing surface area (solids) Adding a catalyst makes a reaction go faster by removing steps from the mechanism and lowering the activation energy without getting used up in the process. (c) 2006, Mark Rosengarten Heat of Reaction Reactions either absorb PE (endothermic, +DH) or release
PE (exothermic, -DH) Exothermic, PEKE, Temp Endothermic, KEPE, Temp Rewriting the equation with heat included: 4 Al(s) + 3 O2(g) 2 Al2O3(s) + 3351 kJ N2(g) + O2(g) +182.6 kJ 2 NO(g) (c) 2006, Mark Rosengarten Potential Energy Diagrams Steps of a reactions:
Reactants have a certain amount of PE stored in their bonds (Heat of Reactants) The reactants are given enough energy to collide and react (Activation Energy) The resulting intermediate has the highest energy that the reaction can make (Heat of Activated Complex) The activated complex breaks down and forms the products, which have a certain amount of PE stored in their bonds (Heat of Products) Hproducts - Hreactants =(c)DH EXAMPLES 2006, Mark Rosengarten
Making a PE Diagram X axis: Reaction Coordinate (time, no units) Y axis: PE (kJ) Three lines representing energy (Hreactants, Hactivated complex, Hproducts) Two arrows representing energy changes: From Hreactants to Hactivated complex: Activation Energy From Hreactants to Hproducts : DH ENDOTHERMIC PE DIAGRAM EXOTHERMIC PE DIAGRAM
(c) 2006, Mark Rosengarten Endothermic PE Diagram If a catalyst is added? (c) 2006, Mark Rosengarten Endothermic with Catalyst The red line represents(c)the catalyzed reaction. 2006, Mark Rosengarten Exothermic PE Diagram
(c) 2006, Mark Rosengarten What does it look like with a catalyst? Exothermic with a Catalyst The red line represents the catalyzed reaction. Lower 2006, Mark Rosengarten A.E. and faster reaction(c)time! Equilibrium
When the rate of the forward reaction equals the rate of the (c) 2006, Mark Rosengarten reverse reaction. Examples of Equilibrium Solution Equilibrium: when a solution is saturated, the rate of dissolving equals the rate of precipitating. NaCl (s) Na+1 (aq) + Cl-1 (aq) Vapor-Liquid Equilibrium: when a liquid is trapped with air
in a container, the liquid evaporates until the rate of evaporation equals the rate of condensation. H2O (l) H2O (g) Phase equilibrium: At the melting point, the rate of solid turning to liquid equals the rate of liquid turning back to solid. H2O (s) H2O (l) (c) 2006, Mark Rosengarten Le Chteliers Principle If a system at equilibrium is stressed, the equilibrium will
shift in a direction that relieves that stress. A stress is a factor that affects reaction rate. Since catalysts affect both reaction rates equally, catalysts have no effect on a system already at equilibrium. Equilibrium will shift AWAY from what is added Equilibrium will shift TOWARDS what is removed. This is because the shift will even out the change in reaction
rate and bring the system back to equilibrium NEXT (c) 2006, Mark Rosengarten Steps to Relieving Stress 1) Equilibrium is subjected to a STRESS. 2) System SHIFTS towards what is removed from the system or away from what is added. The shift results in a CHANGE OF CONCENTRATION for both the products and the reactants. If the shift is towards the products, the concentration of the
products will increase and the concentration of the reactants will decrease. If the shift is towards the reactants, the concentration of the reactants will increase and the concentration of the products will decrease. NEXT (c) 2006, Mark Rosengarten Examples For the reaction N2(g) + 3H2(g) 2 NH3(g) + heat
Adding N2 will cause the equilibrium to shift RIGHT, resulting in an increase in the concentration of NH 3 and a decrease in the concentration of N2 and H2. Removing H2 will cause a shift to the LEFT, resulting in a decrease in the concentration of NH3 and an increase in the concentration of N2 and H2. Increasing the temperature will cause a shift to the LEFT, same results as the one above. Decreasing the pressure will cause a shift to the LEFT, because there is more gas on the left side, and making more gas will bring the pressure back up to its equilibrium amount. (c) 2006, Adding a catalyst will
haveMark no Rosengarten effect, so no shift will happen. Solubility Curves Solubility: the maximum quantity of solute that can be dissolved in a
given quantity of solvent at a given temperature to make a saturated solution. Saturated: a solution containing the maximum quantity of solute that the solvent can hold. The limit of solubility. Supersaturated: the solution is holding more than it can theoretically hold OR there is excess solute which precipitates out. True supersaturation is rare. Unsaturated: There are still solvent molecules available to dissolve more solute, so more can dissolve. How ionic solutes dissolve in water: polar water molecules attach to the ions and tear them off the crystal. (c) 2006, Mark Rosengarten
Solubility Solubility: go to the temperature and up to the desired line, then across to the Y-axis. This is how many g of solute are needed to make a saturated solution of that solute in 100g of H2O at that particular temperature. At 40oC, the solubility of KNO3 in 100g of water is 64 g. In 200g of water, double that amount. In 50g of water, cut it in half. (c) 2006, Mark Rosengarten
Supersaturated If 120 g of NaNO3 are added to 100g of water at 30oC: 1) The solution would be SUPERSATURATED, because there is more solute dissolved than the solubility allows 2) The extra 25g would precipitate out 3) If you heated the solution up by 24oC (to 54oC), the excess solute
would dissolve. (c) 2006, Mark Rosengarten Unsaturated If 80 g of KNO3 are added to 100g of water at 60oC: 1) The solution would be UNSATURATED, because there is less solute dissolved than the solubility allows 2) 26g more can be added to make a saturated solution
3) If you cooled the solution down by 12oC (to 48oC), the solution would become saturated (c) 2006, Mark Rosengarten How Ionic Solutes Dissolve in Water Water solvent molecules attach to the Water solvent holds the ions apart and (c) 2006, Mark
Rosengarten ions (H end to the Cl-, O end to the Na+) keeps the ions from coming back together Acids and Bases 1) Formulas, Naming and Properties of Acids 2) Formulas, Naming and Properties of Bases 3) Neutralization 4) pH 5) Indicators 6) Alternate Theories (c) 2006, Mark Rosengarten
Formulas, Naming and Properties of Acids Arrhenius Definition of Acids: molecules that dissolve in water to produce H3O+ (hydronium) as the only positively charged ion in solution. HCl (g) + H O (l) H O+ (aq) + Cl2 3 Properties of Acids Naming of Acids Formula Writing of Acids (c) 2006, Mark Rosengarten
Properties of Acids Acids react with metals above H2 on Table J to form H2(g) and a salt. Acids have a pH of less than 7. Dilute solutions of acids taste sour. Acids turn phenolphthalein CLEAR, litmus RED
and bromthymol blue YELLOW. Acids neutralize bases. Acids are formed when acid anhydrides (NO2, SO2, CO2) react with water for form acids. This is how acid rain forms from auto and industrial emissions. (c) 2006, Mark Rosengarten Naming of Acids Binary Acids (H+ and a nonmetal) hydro (nonmetal) -ide + ic acid HCl (aq) = hydrochloric acid
Ternary Acids (H+ and a polyatomic ion) (polyatomic ion) -ate +ic acid HNO3 (aq) = nitric acid (polyatomic ion) -ide +ic acid HCN (aq) = cyanic acid (polyatomic ion) -ite +ous acid HNO (aq) = nitrous acid (c) 2006, Mark Rosengarten 2
Formula Writing of Acids Acids formulas get written like any other. Write the H+1 first, then figure out what the negative ion is based on the name. Cancel out the charges to write the formula. Dont forget the (aq) after itits only an acid if its in water! Hydrosulfuric acid: H+1 and S-2 = H2S (aq) Carbonic acid: H+1 and CO3-2 = H2CO3 (aq) Chlorous acid: H+1 and ClO2-1 = HClO2 (aq) Hydrobromic acid: H+1 and Br-1 = HBr (aq) Hydronitric acid: Hypochlorous acid:
Perchloric acid: (c) 2006, Mark Rosengarten Formulas, Naming and Properties of Bases Arrhenius Definition of Bases: ionic compounds that dissolve in water to produce OH- (hydroxide) as the only negatively charged ion in solution. NaOH (s) Na+1 (aq) + OH-1 (aq) Properties of Bases Naming of Bases
Formula Writing of Bases (c) 2006, Mark Rosengarten Properties of Bases Bases react with fats to form soap and glycerol. This process is called saponification.
Bases have a pH of more than 7. Dilute solutions of bases taste bitter. Bases turn phenolphthalein PINK, litmus BLUE and bromthymol blue BLUE. Bases neutralize acids. Bases are formed when alkali metals or alkaline earth metals react with water. The words alkali and alkaline mean basic, as opposed to acidic. (c) 2006, Mark Rosengarten Naming of Bases Bases are named like any ionic
compound, the name of the metal ion first (with a Roman numeral if necessary) followed by hydroxide. Fe(OH)2 (aq) = iron (II) hydroxide Fe(OH)3 (aq) = iron (III) hydroxide Al(OH)3 (aq) = aluminum hydroxide NH3 (aq) is the same thing as NH4OH: NH + H O 3 Rosengarten 2 (c) 2006, Mark
NH4OH Also called ammonium hydroxide. Formula Writing of Bases Formula writing of bases is the same as for any ionic formula writing. The charges of the ions have to cancel out. Calcium hydroxide = Ca+2 and OH-1 = Ca(OH)2 (aq) Potassium hydroxide = K+1 and OH-1 = KOH (aq) Lead (II) hydroxide = Pb+2 and OH-1 = Pb(OH)2 (aq) Lead (IV) hydroxide = Pb+4 and OH-1 = Pb(OH)4 (aq)
Lithium hydroxide = Copper (II) hydroxide = Magnesium hydroxide = (c) 2006, Mark Rosengarten Neutralization H+1 + OH-1 HOH Acid + Base Water + Salt (double replacement) HCl (aq) + NaOH (aq) HOH (l) + NaCl (aq) H SO (aq) + KOH (aq) 2 HOH (l) + K SO (aq) 2 4 2
4 HBr (aq) + LiOH (aq) H CrO (aq) + NaOH (aq) 2 4 HNO (aq) + Ca(OH) (aq) 3 2 H PO (aq) + Mg(OH) (aq) 3 4 2 (c) 2006, Mark Rosengarten
pH A change of 1 in pH is a tenfold increase in acid or base strength. A pH of 4 is 10 times more acidic than a pH of 5. (c) 2006, Mark Rosengarten A pH of 12 is 100 times more basic than a pH of 10. Indicators At a pH of 2:
Methyl Orange = red Bromthymol Blue = yellow Phenolphthalein = colorless Litmus = red Bromcresol Green = yellow Methyl orange is red at a pH of 3.2 and below and yellow at a pH of 4.4 and higher. In between the Thymol Blue = yellow two numbers, it is an intermediate color that is not listed on this table. (c) 2006, Mark Rosengarten
Alternate Theories Arrhenius Theory: acids and bases must be in aqueous solution. Alternate Theory: Not necessarily so! Acid: proton (H+1) donorgives up H+1 in a reaction. Base: proton (H+1) acceptorgains H+1 in a reaction. HNO + H O H O+1 + NO -1 3 2 3 3
Since HNO3 lost an H+1 during the reaction, it is an acid. Since H2O gained the H+1 that HNO3 lost, it is a base. (c) 2006, Mark Rosengarten Oxidation and Reduction 1) Oxidation Numbers 2) Identifying OX, RD and SI Species 3) Agents 4) Writing Half-Reactions 5) Balancing Half-Reactions 6) Activity Series 7) Voltaic Cells 8) Electrolytic Cells
9) Electroplating (c) 2006, Mark Rosengarten Oxidation Numbers Elements have no charge until they bond to other elements. Na0, Li0, H20. S0, N20, C600 The formula of a compound is such that the charges of the elements making up the compound all add up to zero. The symbol and charge of an element or polyatomic ion is called a SPECIES. Determine the charge of each species in the following
compounds: NaCl KNO3 CuSO4 Fe2(CO3)3 (c) 2006, Mark Rosengarten Identifying OX, RD, SI Species Ca0 + 2 H+1Cl-1 Ca+2Cl-12 + H20 Oxidation = loss of electrons. The species becomes more positive in charge. For example, Ca0 Ca+2, so Ca0 is the
species that is oxidized. Reduction = gain of electrons. The species becomes more negative in charge. For example, H+1 H0, so the H+1 is the species that is reduced. Spectator Ion = no change in charge. The species does not gain or lose any electrons. For example, Cl-1 Cl-1, so the Cl-1 is the spectator ion. (c) 2006, Mark Rosengarten Agents Ca0 + 2 H+1Cl-1 Ca+2Cl-12 + H20 Since Ca0 is being oxidized and H+1 is being reduced, the
electrons must be going from the Ca0 to the H+1. Since Ca0 would not lose electrons (be oxidized) if H+1 werent there to gain them, H+1 is the cause, or agent, of Ca0s oxidation. H+1 is the oxidizing agent. Since H+1 would not gain electrons (be reduced) if Ca0 werent there to lose them, Ca0 is the cause, or agent, of H+1s reduction. Ca0 is the reducing agent. (c) 2006, Mark Rosengarten Writing Half-Reactions Ca0 + 2 H+1Cl-1 Ca+2Cl-12 + H20 Oxidation: Ca0 Ca+2 + 2e Reduction: 2H+1 + 2e- H20
The two electrons lost by Ca0 are gained by the two H+1 (each H+1 picks up an electron). PRACTICE SOME! (c) 2006, Mark Rosengarten Practice Half-Reactions Dont forget to determine the charge of each species first! 4 Li + O2 2 Li2O Oxidation Half-Reaction: Reduction Half-Reaction:
Zn + Na2SO4 ZnSO4 + 2 Na Oxidation Half-Reaction: Reduction Half-Reaction: (c) 2006, Mark Rosengarten Balancing Half-Reactions Ca0 + Fe+3 Ca+2 + Fe0 Cas charge changes by 2, so double the Fe. Fes charge changes by 3, so triple the Ca. 3 Ca0 + 2 Fe+3 3 Ca+2 + 2 Fe0 Try these: __Na0 + __H+1 __Na+1 + __H20
(hint: balance the H and H2 first!) __Al0 + __Cu+2 __Al+3 + __Cu0 (c) 2006, Mark Rosengarten Activity Series For metals, the higher up the chart the element is, the more likely it is to be oxidized. This is because metals like to lose electrons, and the more active a metallic element is, the more easily it can lose them.
For nonmetals, the higher up the chart the element is, the more likely it is to be reduced. This is because nonmetals like to gain electrons, and the more active a nonmetallic element is, the more easily it can gain them. (c) 2006, Mark Rosengarten Metal Activity 3 K0 + Fe+3Cl-13 REACTION Fe0 + 3 K+1Cl-1
NO REACTION Metallic elements start out with a charge of ZERO, so they can only be oxidized to form (+) ions. The higher of two metals MUST undergo oxidation in the reaction, or no reaction will happen. The reaction 3 K + FeCl3 3 KCl + Fe WILL happen, because K is being oxidized, and that is what Table J says should happen.
The reaction Fe + 3 KCl FeCl3 + 3 K (c) 2006, Mark Rosengarten will NOT happen. Voltaic Cells Produce electrical current using a spontaneous redox reaction Used to make batteries! Materials needed: two beakers, piece of the oxidized metal (anode, - electrode), solution of the oxidized metal, piece of the reduced metal (cathode, + electrode), solution of the reduced metal, porous material (salt bridge), solution of a salt
that does not contain either metal in the reaction, wire and a load to make use of the generated current! Use Reference Table J to determine the metals to use Higher = (-) anode Lower = (+) cathode (c) 2006, Mark Rosengarten Making Voltaic Cells More Info!!! Create Your
Own (c) 2006, Mark Rosengarten Cell!!!! How It Works Since Zn is listed above Cu, Zn0 will be oxidized when it reacts with Cu+2. The reaction: Zn + CuSO4 ZnSO4 + Cu The Zn0 anode loses 2 e-, which go up the wire and through the load. The Zn0 electrode gets smaller as the Zn0 becomes Zn+2 and dissolves into solution. The e- go into
the Cu0, where they sit on the outside surface of the Cu0 cathode and wait for Cu+2 from the solution to come over so that the e- can jump on to the Cu+2 and reduce it to Cu0. The size of the Cu0 electrode increases. The negative ions in solution go over the salt bridge to the anode side to complete the circuit.(c) 2006, Mark Rosengarten You Start At The Anode Vital to make a battery Is this electrochemistry You take two half-cells And connect them up so well With a load to power in between
You need to have electrodes you see Full of that metallicity Let electrons flow Across the salt bridge we go! Allowing us to make electricity We start the anode Electrons are lost there And go through the wire And through the load on fire They get to the cathode And reduce the cations And the anions go through the salt bridge Back to where
(c) 2006, Mark Rosengarten WHERE? Make Your Own Cell!!! (c) 2006, Mark Rosengarten Electrolytic Cells Use electricity to force a nonspontaneous redox reaction to take place. Uses for Electrolytic Cells: Decomposition of Alkali Metal Compounds
Decomposition of Water into Hydrogen and Oxygen Electroplating Differences between Voltaic and Electrolytic Cells: ANODE: Voltaic (-) Electrolytic (+) CATHODE: Voltaic (+) Electrolytic (-) Voltaic: 2 half-cells, a salt bridge and a load (c) 2006, Electrolytic: 1 cell, no Mark
saltRosengarten bridge, IS the load Decomposing Alkali Metal Compounds 2 NaCl 2 Na + Cl2 The Na+1 is reduced at the (-) cathode, picking up an e- from the battery (c) 2006, Mark Rosengarten
The Cl-1 is oxidized at the (+) anode, the ebeing pulled off by the battery (DC) Decomposing Water 2 H2O 2 H2 + O2 The H+ is reduced at the (-) cathode, yielding H2 (g), which is trapped in the tube.
The O-2 is oxidized at the (+) anode, yielding O (g), which is (c) 2006, Mark Rosengarten 2 trapped in the tube. Electroplating The Ag0 is oxidized to Ag+1 when the (+) end of the battery strips its electrons off. The Ag+1 migrates through
the solution towards the (-) charged cathode (ring), where it picks up an electron from the battery and forms Ag0, which coats on to the (c) 2006, Mark Rosengarten ring. Organic Chemistry 1) Hydrocarbons 2) Substituted Hydrocarbons 3) Organic Families 4) Organic Reactions
(c) 2006, Mark Rosengarten Hydrocarbons Molecules made of Hydrogen and Carbon Carbon forms four bonds, hydrogen forms one bond Hydrocarbons come in three different homologous series: Alkanes (single bond between Cs, saturated) Alkenes (1 double bond between 2 Cs, unsaturated) Alkynes (1 triple bond between 2 Cs, unsaturated) These are called aliphatic, or open-chain, hydrocarbons. Count the number of carbons and add the appropriate
suffix! (c) 2006, Mark Rosengarten Alkanes CH4 = methane C2H6 = ethane C3H8 = propane C4H10 = butane C5H12 = pentane To find the number of hydrogens, double the number of carbons and add 2.(c) 2006, Mark Rosengarten
Methane Meth-: one carbon -ane: alkane The simplest organic molecule, also known as natural gas! (c) 2006, Mark Rosengarten Ethane Eth-: two carbons -ane: alkane
(c) 2006, Mark Rosengarten Propane Prop-: three carbons -ane: alkane Also known as cylinder gas, usually stored under pressure and used for gas grills and stoves. Its also very handy as a fuel for Bunsen burners! (c) 2006, Mark Rosengarten Butane
But-: four carbons -ane: alkane Liquefies with moderate pressure, useful for gas lighters. You have probably lit your gas grill with a grill lighter fueled with butane! (c) 2006, Mark Rosengarten Pentane Pent-: five carbons -ane: alkane Your Turn!!!
Draw Hexane: Draw Heptane: (c) 2006, Mark Rosengarten Alkenes C2H4 = Ethene C3H6 = Propene C4H8 = Butene C5H10 = Pentene To find the number of hydrogens, double the number of carbons.
(c) 2006, Mark Rosengarten Ethene Two carbons, double bonded. Notice how each carbon has four bonds? Two to the other carbon and two to hydrogen atoms. Also called ethylene, is used for the production of polyethylene, which is an extensively used plastic. Look for the PE, HDPE (#2 recycling) or LDPE (#4 recycling) on your plastic bags and containers!
(c) 2006, Mark Rosengarten Propene Three carbons, two of them double bonded. Notice how each carbon has four bonds? If you flipped this molecule so that the double bond was on the right side of the molecule instead of the left, it would still be the same molecule. This is true of all alkenes. Used to make polypropylene (PP, recycling #5), used for dishwasher safe containers and indoor/outdoor carpeting! (c) 2006, Mark Rosengarten
Butene This is 1-butene, because the double bond is between the 1st and 2nd carbon from the end. The number 1 represents the lowest numbered carbon the double bond is touching. This is 2-butene. The double bond is between the 2nd and 3rd carbon from the end. Always count from the end the double bond is closest to. ISOMERS: Molecules that share the same molecular
formula, but have different structural formulas. (c) 2006, Mark Rosengarten Pentene This is 1-pentene. The double bond is on the first carbon from the end. This is 2-pentene. The double bond is on the second carbon from the end. This is not another isomer of pentene. This is also 2-pentene, just that the
is closer to the right end. (c)double 2006, Mark bond Rosengarten Alkynes C2H2 = Ethyne C3H4 = Propyne C4H6 = Butyne C5H8 = Pentyne To find the number of hydrogens, double the number of carbons and subtract 2.
(c) 2006, Mark Rosengarten Ethyne Now, try to draw propyne! Any isomers? Lets see! Also known as acetylene, used by miners by dripping water on CaC2 to light up mining helmets. The carbide lamps were attached to miners helmets by a clip and had a large reflective mirror that magnified the acetylene flame. Used for welding and cutting applications, as ethyne o burns at temperatures
overMark 3000 C! (c) 2006, Rosengarten Propyne This is propyne! Nope! No isomers. OK, now draw butyne. If there are any isomers, draw them too. (c) 2006, Mark Rosengarten
Butyne Well, heres 1-butyne! And heres 2-butyne! Is there a 3-butyne? Nope! That would be 1-butyne. With four carbons, the double bond can only be between the 1st and 2nd carbon, or between the 2nd and 3rd carbons. Now, try pentyne! (c) 2006, Mark Rosengarten Pentyne
1-pentyne 2-pentyne Now, draw all of the possible isomers for hexyne! (c) 2006, Mark Rosengarten Substituted Hydrocarbons Hydrocarbon chains can have three kinds of dingly- danglies attached to the chain. If the dingly-dangly is made of anything other than hydrogen and carbon, the molecule ceases to be a hydrocarbon and becomes another type of organic molecule.
Alkyl groups Halide groups Other functional groups To name a hydrocarbon with an attached group, determine which carbon (use lowest possible number value) the group is attached to. Use di- for 2 groups, tri- for three. (c) 2006, Mark Rosengarten Alkyl Groups (c) 2006, Mark Rosengarten Halide Groups
(c) 2006, Mark Rosengarten Organic Families Each family has a functional group to identify it. Alcohol (R-OH, hydroxyl group) Organic Acid (R-COOH, primary carboxyl group)
Aldehyde (R-CHO, primary carbonyl group) Ketone (R1-CO-R2, secondary carbonyl group) Ether (R1-O-R2) Ester (R1-COO-R2, carboxyl group in the middle) Amine (R-NH2, amine group) Amide (R-CONH2, amide group) These molecules are alkanes with functional groups attached. The name is based on the alkane name. (c) 2006, Mark Rosengarten Alcohol
On to DI and TRIHYDROXY ALCOHOLS (c) 2006, Mark Rosengarten Di and Trihydroxy Alcohols (c) 2006, Mark Rosengarten Positioning of Functional Group PRIMARY (1o): the functional group is bonded to a carbon that is on the end of
the chain. SECONDARY (2o): The functional group is bonded to a carbon in the middle of the chain. TERTIARY (3o): The functional group is bonded to a carbon that is itself directly bonded to three other carbons. (c) 2006, Mark Rosengarten Organic Acid These are weak acids. The H on the right side is the one that ionized in water to form H3O+. The -COOH (carboxyl)
functional group is always on a PRIMARY carbon. Can be formed from the oxidation of primary alcohols using a KMnO4 catalyst. (c) 2006, Mark Rosengarten Aldehyde Aldehydes have the CO (carbonyl) groups ALWAYS on a PRIMARY carbon. This is the only structural difference between aldehydes and ketones. Formed by the oxidation of primary alcohols with a catalyst. Propanal is formed from the oxidation of 1-propanol using pyridinium chlorochromate
(PCC) catalyst.* (c) 2006, Mark Rosengarten Ketone Ketones have the CO (carbonyl) groups ALWAYS on a SECONDARY carbon. This is the only structural difference between ketones and aldehydes. Can be formed from the dehydration of secondary alcohols with a catalyst. Propanone is formed from the oxidation of 2propanol using KMnO4 or PCC catalyst.* (c) 2006, Mark Rosengarten
Ether Ethers are made of two alkyl groups surrounding one oxygen atom. The ether is named for the alkyl groups on ether side of the oxygen. If a three-carbon alkyl group and a fourcarbon alkyl group are on either side, the name would be propyl butyl ether. Made with an etherfication reaction. (c) 2006, Mark Rosengarten Ester Esters are named for the alcohol and organic acid that reacted by esterification to form the ester. If the alcohol was
1-propanol and the acid was hexanoic acid, the name of the ester would be propyl hexanoate. Esters contain a COO (carboxyl) group in the middle of the molecule, which differentiates them from organic acids. (c) 2006, Mark Rosengarten Amine - Component of amino acids, and therefore proteins, RNA and DNAlife itself! - Essentially ammonia (NH3) with the hydrogens replaced by one or more hydrocarbon chains, hence the name amine! (c) 2006, Mark Rosengarten
Amide Synthetic Polyamides: nylon, kevlar Natural Polyamide: silk! For more information on polymers, go here. (c) 2006, Mark Rosengarten Organic Reactions Combustion Fermentation Substitution Addition
Dehydration Synthesis Etherification Esterification Saponification Polymerization (c) 2006, Mark Rosengarten Combustion Happens when an organic molecule reacts with oxygen gas to form carbon dioxide and water vapor. Also known as burning.
(c) 2006, Mark Rosengarten Fermentation Process of making ethanol by having yeast digest simple sugars anaerobically. CO2 is a byproduct of this reaction. The ethanol produced is toxic and it kills the yeast when the percent by volume of ethanol gets to 14%. (c) 2006, Mark Rosengarten
Substitution Alkane + Halogen Alkyl Halide + Hydrogen Halide The halogen atoms substitute for any of the hydrogen atoms in the alkane. This happens one atom at a time. The halide generally replaces an H on the end of the molecule. C2H6 + Cl2 C2H5Cl + HCl The second Cl can then substitute for another H: C2H5Cl + HCl C2H4Cl2 + H2 (c) 2006, Mark Rosengarten Addition
Alkene + Halogen Alkyl Halide The double bond is broken, and the halogen adds at either side of where the double bond was. One isomer possible. (c) 2006, Mark Rosengarten Etherification* Alcohol + Alcohol Ether + Water A dehydrating agent (H2SO4) removes H from one alcohols OH and removes the OH from the other. The two molecules join where there H and OH were removed.
Note: dimethyl ether and diethyl ether are also produced from this reaction, but can be separated out. (c) 2006, Mark Rosengarten Esterification Organic Acid + Alcohol Ester + Water A dehydrating agent (H2SO4) removes H from the organic acid and removes the OH from the alcohol. The two molecules join where there H and OH were removed. (c) 2006, Mark Rosengarten
Saponification The process of making soap from glycerol esters (fats). Glycerol ester + 3 NaOH soap + glycerol Glyceryl stearate + 3 NaOH sodium stearate + glycerol The sodium stearate is the soap! It emulsifies grease surrounds globules with its nonpolar ends, creating micelles with - charge that water can then wash away. Hard water replaces Na+ with Ca+2 and/or other low solubility ions, which forms a precipitate called soap scum. Water softeners remove these hardening ions from your tap water, allowing the soap to dissolve normally. (c) 2006, Mark Rosengarten
Polymerization A polymer is a very long-chain molecule made up of many monomers (unit molecules) joined together. The polymer is named for the monomer that made it. Polystyrene is made of styrene monomer Polybutadiene is made of butadiene monomer Addition Polymers
Condensation Polymers Rubber (c) 2006, Mark Rosengarten Addition Polymers Joining monomers together by breaking double bonds Polyvinyl chloride (PVC): vinyl siding, PVC pipes, etc. Vinyl chloride n C2H3Cl polyvinyl chloride
-(-C2H3Cl-)-n Polytetrafluoroethene (PTFE, teflon): TFE n C2F4 PTFE -(-C (c) 2006,
2FMark 4-)-Rosengarten n Condensation Polymers Condensation polymerization is just dehydration synthesis, except instead of making one molecule of ether or ester, you make a monster molecule of polyether or polyester. (c) 2006, Mark Rosengarten Rubber
The process of toughing rubber by cross-linking the polymer strands with sulfur is called... (c) 2006, Mark Rosengarten VULCANIZATION!!! (c) 2006, Mark Rosengarten THE END (c) 2006, Mark Rosengarten