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NA = 6.022 x 1023 °C = (5/9) (°F - 32) °F = (9/5)(°C) + 32
1 amu = 1.661 x 10-27 kg °C = K - 273.15 K = °C + 273.15
1 atm = 760 torr = 760 mm Hg 1 atm = 1.013 bar pV = nRT
R = 0.08206 L.atm/mol.K 1 L.atm = 101.3 J 1 amp = 1 C/s
R = 8.314 J/mol.K 1 J= 1 kg.m2/s2 (1 volt) (1 Coulomb) = 1 Joule
pA = XA pA° [B] = KB pB DpA = XBpA°
DTb = Kb mB DTf = Kf mB P = [B]RT
[A]t = [A]0 e-kt ln[A]t = ln[A]0 - kt t1/2 = ln2/k
[A]t = [A]0/(1 + kt[A]0) (1/[A]t) = (1/[A]0) + kt t1/2 = 1/(k[A]0)
k = A e-Ea/RT ln k = ln A - (Ea/R)(1/T) ln(k2/k1) = - (Ea/R) [ (1/T2) - (1/T1) ]
If ax2 + bx + c = 0, then x = ( - b ± [b2 - 4ac]1/2 )/2a
KP = Kc (RT)Dn Ka.Kb = Kw = 1.0 x 10-14 (at T = 25°C)
pH = pKa + log10{[base]/[acid]}
H = E + pV G = H - TS F = 96485. C/mol
DGrxn = DG°rxn + RT ln Q ln K = - DG°rxn/RT
DG = - nFE E = E° - (RT/nF) ln Q ln K = nFE°/RT
GENERAL CHEMISTRY 2
FINAL EXAM
JUNE 18, 2009
Name ______
Panthersoft ID ______
Signature ______
Part 1 ______(40 points)
Part 2 ______(60 points)
Part 3 ______(50 points)
TOTAL ______(150 points)
Do all of the following problems. Show your work.
Part 1. Multiple choice. Circle the letter corresponding to the correct answer. There is one and only one correct answer per problem. [5 points each]
1) A solution is formed by mixing 0.0200 moles of NaBr, a nonvolatile solute, and 500.0 g of water. Which of the following statements about this solution is correct?
a) The equilibrium partial pressure of water above the solution is larger than the equilibrium partial pressure of water above pure water
b) The boiling point of the solution is larger than the boiling point of pure water
c) The freezing point of the solution is larger than the freezing point of pure water
d) Both a and b
e) Both a and c
2) A particular chemical reaction obeys the rate law rate = k [A] [B]2. If the initial concentration of A and the initial concentration of B are both doubled, the initial rate of reaction
a) will be the same
b) will increase by a factor of 2
c) will increase by a factor of 4
d) will increase by a factor of 8
e) none of the above
3) Consider the following gas phase reaction in a closed system at constant temperature and volume.
Cl2(g) + Br2(g) D 2 ClBr(g)
A system initially not at equilibrium has QC < KC. Which of the following will occur as the system approaches equilibrium
a) The number of moles of Cl2 in the system will increase
b) The number of moles of Cl2 in the system will remain constant
c) The number of moles of Cl2 in the system will decrease
d) Either a or b
e) Either b or c
4) Consider the following three substances: HBrO3, HBrO4, and HIO3. Which of the following statements concerning these substances is correct?
a) HBrO3 is the strongest acid, HBrO4 is the weakest acid.
b) HBrO3 is the strongest acid, HIO3 is the weakest acid.
c) HBrO4 is the strongest acid, HBrO3 is the weakest acid.
d) HBrO4 is the strongest acid, HIO3 is the weakest acid.
e) HIO3 is the strongest acid, HBrO4 is the weakest acid.
5) Consider the titration of an acid with a base. For which of the following cases do you expect the pH to be approximately equal to 7.0 at the equivalence point of the titration?
a) Titration of a strong acid with a strong base.
b) Titration of a weak acid with a strong base.
c) Titration of a weak base with a strong acid.
d) Both b and c.
e) Both a and b and c.
6) A chemical reaction is carried out at a constant temperature and pressure. If the reaction is spontaneous, which of the following must be true?
a) DSrxn < 0
b) DGrxn < 0
c) DHrxn < 0
d) Both a and b
e) Both a and c
7) Oxidation occurs at the cathode
a) For neither a galvanic cell nor an electrolytic cell.
b) For a galvanic cell, but not for an electrolytic cell.
c) For an electrolytic cell, but not for a galvanic cell.
d) For both a galvanic cell and an electrolytic cell.
e) Cannot tell from the information given.
8) Zinc metal can be produced from the reduction of Zn2+ ion by the following half reaction
Zn2+(aq) + 2 e- ® Zn(s)
How many Coulombs of electrons are needed to produce 1.00 mol of Zn metal from Zn2+ ion?
a) 1 Coulomb of electrons
b) 2 Coulombs of electrons
c) 96485 Coulombs of electrons
d) 192970 Coulombs of electrons
e) None of the above
Part 2. Short answer.
1) A solution is prepared by combining 36.82 g of benzene (C6H6, MW = 78.1 g/mole) and 595.8 g of toluene (C7H8, MW = 92.1 g/mole). What is mben, the molality of benzene, in the above solution? [9 points]
2) A particular chemical reaction obeys the rate law
rate = k [A]
In a particular experiment the initial concentration of A is [A]o = 0.5418 mole/L. After 10.00 minutes the concentration of A is [A] = 0.3881 mole/L. What is t½, the half-life, for the reaction? Give your answer in units of minutes.
[10 points]
3) The equilibrium constant for the reaction
3 H2(g) + N2(g) D 2 NH3(g)
is Kc = 4.3 x 108 at T = 25. °C.
A system at T = 25. °C initially contains 0.200 mole/L of ammonia (NH3(g)). No nitrogen (N2(g)) or hydrogen (H2(g)) is initially present. What is the concentration of H2(g) in the system be when equilibrium is reached?
[10 points]
4) Answer each of the following questions by filling in the blank. [5 points each]
a) The conjugate base of HCO3-. ______
b) The value for Kb for ClO-., at T = 25. °C ______
(Note Ka = 3.5 x 10-8 for HOCl at T = 25. °C)
c) The pH of pure water at T = 50.°C. ______
(Note Kw = 5.5 x 10-14 at T = 50.°C)
5) Balance the following unbalanced oxidation-reduction reactions [8 points each]
a) SO32-(aq) + MnO4-(aq) ® SO42-(aq) + Mn2+(aq) (for acid conditions)
b) Al(s) + NO2-(aq) ® AlO2-(aq) + NH3(aq) (for base conditions)
Part 3. Problems.
1) A solution is prepared by dissolving 2.6818 g of a protein in benzene (C6H6). The final volume of the solution is V = 200.0 mL. The osmotic pressure of the polymer solution, measured at T = 15.0 °C, is P = 34.8 torr. Based on this information what is the molecular weight of the protein? [10 points]
2) Consider the following titration at T = 25. °C. A 20.00 mL of a 0.2000 M solution of hypochlorous acid (HClO, Ka = 3.5 x 10-8), a weak monoprotic acid, is titrated with a 0.1000 M solution of potassium hydroxide (KOH), a strong base.
a) What is the initial pH of the hypochlorous acid solution? [8 points]
b) What is the pH of the solution at the equivalence point of the titration? [12 points]
3) Several half-cell reduction reactions are given below (for T = 25. °C) and may be of usein doing the following problem.
Reaction E°(v)
Cu2+(aq) + 2 e- ® Cu(s) + 0.34
Bi3+(aq) + 3 e- ® Bi(s) + 0.20
2 H+(aq) + 2 e- ® H2(g) 0.00
Sn2+(aq) + 2 e- ® Sn(s) - 0.14
Ni2+(aq) + 2 e- ® Ni(s) - 0.23
Zn2+(aq) + 2 e- ® Zn(s) - 0.76
a) Give one substance from the abve list capable of reducing Sn2+ to Sn for standard conditions. [4 points]
______
b) Consider the following galvanic cell at T = 25. °C.
Ni(s)|Ni2+(aq)||Bi3+(aq)|Bi(s)
What is the half-cell oxidation reaction, the half-cell reduction reaction, the net cell reaction, and the standard cell potential corresponding to the above galvanic cell? [8 points]
c) The above galvanic cell is operated under conditions where [Ni2+] = 0.100 mole/L and [Bi3+] = 0.0020 mole/L. What is the cell potential for this set of conditions? [8 points]
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