Chemistry Study Guide (Exam 2)

Examination 2 Chapters 4,5, and 6 Study Guide Chapter 4 Chemical Quantities and Aqueous reactions * Reactions Stoichiometry * jettye-mole conversions * mass-mass conversions * modification Reactants * What is the Limiting Reagent * How do we find the L. R. * Solutions * Molarity rendering and how to calculate * Dilutions Calculations (M1V1 = M2V2, c areful with M2) * Solution Stoichiometry * volume-volume conversions * volume-mass conversions * molecular interpretation of solubility * solubility rules * Precipitation Reactions * Determining reaction products * Following solubility rules Molecular Formula, Total noggin formula, net ionic formula * Acid-Base Reactions * oxidation-reduction reactions * Identify odixation states * Identify which species was oxidized and trim Chapter 5 Gases * Pressure definition * Simple Gas impartialitys * Boyles Law pV * Charless Law P/T * Avogadros Law nT * Ideal Gas Laws * pV=nRT * niggardness calculations * Molar Mass calculations * Molar Volume * Partial Pressures * Daltons Law of Partial Pressures * Eudometer calculations * Gas Reaction Stoichiometry * Volume moles conversions * Kinetic Molecular Theory * 4 genes of the hypothesis * You DO NOT need to know the derivation of I.G. L. * Effusion of Gases * Real Gases * van der Waals equating * Your extra credit scruple will have to do with this topic * Atmospheric Chemistry * 3 types of pollution-very, very basic question Chapter 6 Thermochemistry * spirit of Energy * System versus touchs * Definition of Energy, internal nada, law of conservation of competency * 1st Law of Thermodynamics * ? E = q + w * Sign convention, (is it positive or negative) * Heat and field of study * pV puddle * m Cs ? T commove transfer * conservation of thermal energy * Calorimetry * Constant volume calorimetry * only change contributes to ? E * Enthalpy * Definition, par Calculation using incessant pressure calorimetry * Exothermic versus Endothermic reactions (sign of ? H) * Hesss Law * Enthalpy of reactions manipulations * This is a hard topic, please, please, please revaluation this after Wednesday Examination 2 Chapters 4, 5, and 6 Study Guide Chapter 4 Chemical Quantities and Aqueous Reactions * Reactions Stoichiometry * mole-mole conversions * Needs a balanced chemical equation * ** over again no decease examples. Let me know if you can find any** * mass-mass conversions * **No clear examples. Let me know if you can find any** * Limiting Reactants * What is the Limiting Reagent The limiting reagent is also known as the limiting reactant. It is the reactant that limits the measuring stick of product in a chemical reaction. Notice that the limiting reactant is the reactant that makes the least amount of product. * How do we find the L. R. * Example * How many grams of N2 (g) can be produced from 9. 05 g of NH3 (g) reacting with 45. 2 g of CuO (s)? Create and Balance a Chemical Equation 2NH3 (g) + 3CuO (g) N2 (g) + 3Cu (S) + 3 piss (l) 9. 05 g NH3 x 1 mol NH3 x 1 mol N2 x 28. 02 N2 = (7. 44 g N2) 17. 04 g NH3 2 mol NH3 1 mol N2 45. 2 g CuO x 1 mol CuO x 1 mol N2 x 28. 2 N2 = (5. 31 g N2 Less = LR Cuo is the Limiting Reactant * Solutions * Morality definition and how to calculate * Definition * Amount of solute (in moles) per amount of solution (in Liters) * Molarity (M) = Amount of Solute (in moles) Amount of Solution (in L) * **Side Note** * Homogenous Mixture = solutions (Salt Water) * Solvent (a component in a solution) Majority component, what something is dissolved in. (Water) * Solute (another component in a solution) Minority component, what is being dissolved (salt) * Example What is the poor boyity of a solution containing 3. 4 g of NH3 (l) in 200. 00 mL of solution? Given 3. 4 g of NH3M = moles of solute (NH3) 200. 00 mL L of Solution (200. 00 mL) Convert 3. 4 g NH3 X 1 mol NH3 = (0. 20 mols NH3) 17. 04 G nh3 200 mL X 1 L = (0. 2L) 1000 mL M = 0. 20 mols NH3 / 0. 2 L = 1. 0 M NH3 **More examples in N otes ** * Dilutions Calculations (M1V1 = M2V2, careful with M2) * Diluting a solution is a common practice and the number of moles of solute will not change (M1)(V1) = (M2)(V2) * Examples What is the concentration of a solution prepared by diluting 45. mL of 8. 25 M HNO3 to 135. 0 mL? M1V1 = M2V2 8. 25 M HNO3 X 0. 045 L = M2 X 0. 135 L 0. 135 L 0. 135 L M2 = 275 M HNO3 * Solution Stoichiometry * volume-volume conversions * When using morality, you can easily extract moles * With a balance chemical equation, you can metamorphose between amounts of substances. * Exampes Look at notes OR page 145 TB * volume-mass conversions * Examples Look at notes OR page 145 TB * **This wasnt clear and If you know what this means, let me know. Or else I will ask Donavan on Saturday (Because there wasnt a specific section for the two bullet points) Molecular interpretation of solubility * solubility rules be familiar with the chart/table that Prof. Donavan gave out 2 interactive forces that affec t solubility 1. solute-solute interaction 2. solute-solvent interaction if solute-solvent interactions are strong enough, solute will dissolve (solute-solvent interaction solute-solute interaction) * Precipitation Reactions * Determining reaction products General Form AX (aq) + BY (aq) AY (aq) + BX (s) Example 2KI (aq) + Pb (NO3)2 (aq) 2KNO3 (aq) + PbI2 (s) * Following Solubility rules Molecular Formula, Total ionic formula, net ionic formula Examples Molecular Formula 2KOH (aq) + Mg(NO3)2 (aq) 2KNO3 (aq) + Mg(OH)2 (s) Total ionic formula * 2K+ (aq) + 2(OH) (aq) + Mg2+ (aq) + 2(NO3) (aq) 2K+ (aq) + 2(NO3)- (aq) + Mg(OH)2(s) Net Ionic formula (remove each spectator ions ions that are aqueous as reactants and stay aqueous when they turn into products) Mg2+(aq) + 2(OH)-(aq) Mg(OH)2(s) * Acid-Base Reactions General Form HA (aq) + BOH (aq) H2O (l) + BA (aq) Example HCl (aq) + NaOH (aq) H2O (l) + NaCl (aq) * Oxidation-Reduction reactions Oxidation is the loss of electrons * Redu ction is the gain of electrons * Oxidation states charges that allow us to keep track of electrons in chemical reactions * Identify oxidation states 1. Charge states of torpid compounds are zero 2. Charge of atoms in polyatomic ions need to add up to the total charge of the polyatomic 3. Keep Alkali metals as +1 alkali earth metals as +2 4. Keep F (fluorines) as -1 H as +1 O as -2 * Identify which species was oxidized and reduced * Look in last section of Chapter 4 Notes Chapter 5 Gases * Pressure definition Pressure The force per unit area * Pressure comes from the constant interaction with a container * Standard Pressure = Normal Atmospheric Pressure * 760. 0 mm Hg = 1 ambience * 760. 0 torr = 1 ambiance * 1. 000 atm * 101, 325 pa (pascals) = 1 atm * 14. 7 psi (lbs per square inch) = 1 atm * Example * (45. 0 psi) x (101, 325 pa) x (1 k pa) _____________________________ = 310. kPa (14. 7 psi) x (1000 pa) * Simple Gas Laws * Boyles Law pV * The volume of a gas inversely proport ional to its pressure, provided the temperature and quantity of gas dont change. * V= k/p Actual Equation pV= K * Example A balloon is put in a bell jar and the pressure is reduced from 782 torr to 0. viosterol atm. If the volume of the balloon is now 2. 78 x 103 mL, what was it originally? V1 = 782 torr x 1. 000 atm/760 torr = 1. 03 atm (1. 03 atm)(V1) = (. 500 atms)(2. 78 x 103 mL) After Rearranging the equation V1= 1350 mL or 1. 35 x 103 mL * Charless Law P/T * The volume of a gas is diretly proportional to its temperature, provided the pressure and quantity of the gas that dont change. (V= KT) **Temp in Kelvin Only** * For changes in Volume (involving temperature) * V1/T1 = V2/T2 For Changes in Pressure * P/T (initial) = P/T (final) * Example (LOOK IN NOTES ) * Avogadros Law nT * The volume of a gas is directly proportional to the quantity of gas, provided the pressure and temperature of the gas dont change. (V=Kn) * For changes in volume (involving moles) * V1/n1 = V2/n2 * E xample (LOOK IN NOTES ) * Ideal Gas Laws * pV=nRT * NEED TO KNOW THIS FORMULA * P = pressure (atm) * V = volume (L) * n = quantity (moles) * T = temperature (K) * R = Universal Gas Constant * (0. 08206 Latm/molK) OR * (8. 314 J/molK) * Example (look in notes ) Density calculations * Density of a gas STP * For an Ideal gas STP, the molar volume = 22. 7 L * Density = mass/volume = mass/1mole = molar mass/molar volum * volume/1mole * Density for a gas NOT STP * If gas isnt at stp * Then D = P(MM)/ RT or D = m/v * Molar Mass calculations * From the equations pV = mRT/MM You get MM = mRT/ pV * Example (Look in notes ) * Molar Volume * At STP, all angel gases tax return up the same volume. * Molar Volume = of L of gas 1 mole of gas This also works V/n = RT/P * Partial Pressures Daltons Law of Partial Pressures * The total pressure of a mixture of gases is the sum of the pressures by each gas. * The pressure of a gas would exert if it were solo in a container. * You can calculate th e Partial Pressure from Ideal gas Law * If 2 gases , A and B are mixed together * P(A) = (nA)(R)(T)/ (V) and P(B) = (nB)(R)(T)/ (V) * Since R, T, and V are all constant for a mixture * P(total) = P(A) + P(B) = (nTotal)(R)(T)/ (V) * nTotal = sum of nA + nB * Example (Look in notes ) Eudiometer calculations * An Eudiometer is a gas collecting electron tube * Example 2Zn (s) + 6HCl (aq) 3H2 (g) + 2ZnCl3 (aq) H20 (l) H2O (g) P(total) = P(H2) + P(H20) (value may be looked up at table 5. 4) * 0. 12 moles of Hz is collected over H20 in a total 10. 0 L container at 323 K. Find the total pressure. P = nRT/V P(H2) = (0. 12 mol H2) (0. 08206 Latm/molK) (323 K)= 0. 3181 am (10. 0L) P(total) = P(H2) + P(H20) P(H2O) 50 degrees Celsius = 92. 6 mmHg P(total) = 240mmHg + 96. 6mmHg = 330mmHg * Gas Reaction Stoichiometry * General notion plan on most problems P, V, T of Gas A Amount A (in moles) Amount B (in moles) P, V, T of Gas B * Volume moles conversions * Ex Methanol CH3OH can be synthesised by the following reaction * CO2 (g) + 2H2(g) CH3OH(g) * What is the volume (in liters) of hydrogen gas a temperature of 355 K and pressure of 738 mmHG, is required to synthesize 35. 7 g of methanol * Given 35. 7 g CH3OH temp 355 K pressure 738 mmHG * Find V of H2 * 1. G of CH3OH mols * 35. 7g CH3OH x 1 mol CH3OH = 1. 1142 mol CH3OH 31. 04 g CH3OH * 2. Mol CH3OH mol H2 * 1. 11 mol CH3OH x 2 mols H2 = 2. 23 mols H2 1 mol CH3OH 3. N(mol H2), P, T VH2 * Convert your mmhg to ATM, and get . 971 atm * VH2= (2. 23 mol H2) (. 08206 l atm/ mol K) (355 K) = 66. 9 L .971 atm * VH2= 66. 9 L * Kinetic Molecular Theory * In this theory a gas is modeled as a collection of particles (either molecules or atoms depending on the gas ) in constant motion. * Ex, a single particle moves in a straight line until it collides with another particle (or with the walls of its container). * 4 components of the theory 1. Particles are infinitely small and have no volume 2. Average energising energy of a partic le is proportional to the temperature (k). . Particles travel in two straight lines following Newtonian Laws 4. All collisions are elastic (no attractive or repulsive forces) * You DO NOT need to know the derivation of I. G. L. * Effusion of Gases * Effusion the process by which a gas escapes from a container into a nothingness through a small hole. * The rate of effusion (the amount of gas that effuses in an amount of time) is also related to the root mean square f number * Rate is ? 1M * Grahms law of effusion * The ratio of effusion rates of two different gases. * For example (look in notes, end of chapter 5) Real Gases * van der Waals equation is an equation used to correct for the discrepancies from the Kinetic Molecular Theory that real gases undergo. Real gases attract each other, therefore, real pressure ideal pressure. Real gases also take up space, therefore, real volume ideal volume. P + a (n/v)? x (V nb) = nRT where a corrects for molecular interaction. It makes t he real pressure larger so it equals the ideal pressure b corrects for molecular size. It decreases the volume of the container. * Your extra credit question will have to do with this topic * Atmospheric Chemistry 3 types of pollution-very, very basic question * 3 types of pollution-very, very basic question 1. Hydrocarbon combustion for automobiles 2C8H18 + 2SO2 16CO2 + 18 H2O At high temperature, nitrogen can also be combusted, which causes a problem. N2 + O2 2NO 2NO + O2 2NO2 (nitrogen dioxide) photochemical smog (causes problem in the environment) 2. Combustion of coal from power plants (Ex. Electrical cars) C + O2 CO2 (Coal contains a significant amount of sulfur and it further combusts) S8 + 8O2 2SO3 2SO2 + O2 2SO3 SO3 + H2O H2SO4 (H2SO4 results to acidification)But, people have found a way to eliminate the production of SO3 and that is by using clean coal and scrubbers. CaCO3 + SO2 CaO + CO2 CaO + SO2 CaSO3 (s) (calcium sulfite) 3. Stratospheric Ozone O3 + UV O2 + O (oxygen radical) O2 + O O3 + IR These two equations above just shows how ozone is used and how it is just regenerated again. But, in 1974, Sherwood Rowland discovered that CFCs from air conditioners, refrigerators, and spray cans destroy the atmospheric ozone. CF2Cl2 + UV CF2Cl + Cl (chlorine radical) Cl + O3 + UV O2 + ClO ClO + O O2 + Cl ( 1 Cl radical can destroy a hundred thousands of ozone)Practice testanswer keyChapter 6 Thermochemistry * character of Energy * System versus Surroundings System the part of the universe we want to focus on (like a chemical reaction inside a beaker) Surrounding everything else in the universe (like the glass of the beaker and the air around it) * Definition of Energy, internal energy, law of conservation of energy Energy is classified into two types a. heat (q) energy transferred that causes a temperature change (due to a change in the random motion of molecules) b. work (w) energy transferred that causes an object to move (due to a ch ange in the design motion of the molecules in the object) c. nits of energy I. Joule (J) the amount of energy it take to move 1kg mass a distance of 1 meter (unit kg*m2/s2) II. large calorie (cal) the amount of energy needed to raise the temperature of 1 gram of water by 1 ? C 1 kcal = 1000 cal (food calories) 1 cal = 4. 184 J (exact measurement) congenital Energy total energy of a system. (Esystem) Law of conservation of energy energy is neither created or destroyed, only transferred. * 1st Law of Thermodynamics The change in energy of a system is equal to heat that enters the system plus the work done on the system. * ? E = q + w a. ?E = change in the internal energy of a system E is (+) if the energy is absorbed by the system ?E is (-) if the energy is released by the system b. q = heat q is (+) if the heat is absorbed by the system q is (-) if the heat is released by the system c. w = work w is (+) if the work is done on the system w is (-) if the work is done by the sys tem on the surrounding * Heat and work * pV work is defined by the equation w = -p? V * m Cs ? T heat transfer q = m Cs ? T where m = mass Cs = specific heat capacity (J/ g ? C) ?T = (Tfinal Tinitial) q = n Cm ? T where n = number of moles Cm = molar heat capacity (J/ mol ? C) ?T = (Tfinal Tinitial) conservation of thermal energy the amount of energy that is given must be equal with opposite sign to that energy that is being taken. qsurr = (qsys) msurr Cs(surr) ? T(surr) = -msys Cs(sys) ? Tsys * Calorimetry * Constant volume calorimetry * Constant volume calorimetry bomb calorimetry, no pv work done, therefore only heat contributes to ? E qcal = Ccal ? T = -qrxn where Ccal = calorimeter constant (KJ/ ? C) * * only heat contributes to ? E * Enthalpy * Definition, equation Enthalpy (? H) the heat absorbed or released during a process taking place at a constant external pressure. ?H = qrxn = -qsurr ?H = -( m Cs ? T) Calculation using constant pressure calorimetry refer to exa mple in notes * Exothermic versus Endothermic reactions (sign of ? H) Endothermic reactions have (+) ? H because they are reactions that absorb heat. Exothermic reactions have (-) ? H because they are reactions that give off heat. * Hesss Law * Enthalpy of reactions manipulations 2 rules to remember 1. If a reaction is reversed, the sign of ? H flips (from negative to positive or from positive to negative) 2. If you reckon coefficients by a number, ? H is also multiplied by that number. * This is a hard topic, please, please, please review this after Wednesday