1.) The change in pH at the equivalence point in the titration of a strong acid with a strong base is
______the change in pH at the equivalence point in the titration of a weak acid with a
strong base.
a) smaller and less sharp than
b) larger but less sharp than
c.) larger and sharper than
d) exactly the same as
2.) Which values of ⊗G, Ecell, and Keq are consistent with spontaneous processes? (The values in an answer
are not necessarily consistent with each other, and you are not being asked to assess whether they are
consistent with each other.)
a. G = -42 kJ; Ecell = +0.42 V; Keq = 0.42
b. G = -42 kJ; Ecell = +0.42 V; Keq = 4.2
c. G = +42 kJ; Ecell = -0.42 V; Keq = -0.42
d G = +42 kJ; Ecell = +0.42 V; Keq = 4.2
3.) What change will be caused by addition of a small amount of HCl to a solution containing fluoride ions and hydrogen fluoride?
a) The concentration of hydronium ions will increase significantly.
b) The concentration of fluoride ions will increase as will the concentration of hydronium ions.
c) The concentration of hydrogen fluoride will decrease and the concentration of fluoride ions will increase.
d) The concentration of fluoride ion will decrease and the concentration of hydrogen fluoride will increase.
e) The percent of ionization of hydrogen fluoride will increase.
4.) Which one of the following reactions is a redox reaction?
a) K2CrO4 + BaCl2 → BaCrO4 + 2KCl
b) Pb2+ + 2Br– → PbBr2
c) Cu + S → CuS
d) None of the above
5.) (4 pts) A solution containing which one of the following pairs of substances will be a buffer solution?
a) NaI, HI
b) KBr, HBr
c) RbCl, HCl
d) CsF, HF
e) none of the above
6.) Considering the E0red values given, which is the strongest reducing agent?
a) Mg E = -2.37
b) Cu E = +0.34
c) Zn E= -0.76
d) Ag E = +0.80
7.) What is the oxidizing agent in the following reaction?
2MnO4–(aq) + 5Ni(s) + 16H+(aq) → 2Mn2+(aq) + 5Ni2+(aq) + 8H2O(l)
a) Mn in MnO4–
b) Ni
c) H+
d) There is no oxidizing agent in this reaction
8.) Which of the following is the best oxidizing agent?
a.) Mg E = -2.37
b.) I2 E = +0.54
c.) Zn2+ E = -0.76
d.) F2 E = +2.87
e.) None of the above are oxidizing agents
9.). Using the Ka values listed, which of the following would be best suited to make a
buffer at pH 7?
a.) H3PO4(aq) and H2PO4- Ka (H3PO4 = 7.53E-3)
b.) HCN(aq) and CN-(aq) Ka (HCN) = 6.17E-10
c.) H2PO4- (aq) and HPO4 2- (aq) Ka(H2PO4-) = 6.23E-8
d.) HNO2(aq) and NO2-(aq) Ka (HNO2) = 4.0E-4
10.) Under which of the following conditions is the reaction spontaneous and enthalpy driven?
a.) △S is negative and △H is negative at low temperatures
b.)△S is negative and △H is negative at high temperatures
c.) △S is positive and △H is positive at low temperatures
d.) △S is positive and △H is positive at high temperatures
11.) For each of the following pairs choose the substance with the higher entropy
a. Ar (l) or Ar (g)
b. He (g) at 3 atm or He (g) at 1.5 atm
c. 1 mol of Ne (g) in 15 L or 1 mol Ne (g) in 1.5 L
d. 1 mol P4 (g) at 300˚ C & 0.01 atm or 1 mol As4 (g) at 300˚ C & 0.01 atm
Problems:
1.) A certain constant-pressure reaction is nonspontaneous at 45 °C. The entropy change for the reaction is 72 J/K. What can you conclude about the sign and magnitude of ΔH?
2.) The Kb = 4.4*10-4 for methylamine (CH3NH2) at 25 °C.
a.)Write the chemical equation for the equilibrium that corresponds to Kb.
b)By using the value of Kb, calculate ΔG° for the equilibrium in part a.
c) What is the value of ΔG at equilibrium?
d.) What is the value of ΔG when [H+] = 6.7 * 10-9 M, [CH3NH3+] = 2.4*10-3 M, and [CH3NH2] = 0.098 M?
3.) A ______Function is independent of the path. These include values such as:
a. ______
b. Pressure
c. ______
d. Entropy
4.) If ΔH= -120.0 kJandΔS= -0.300kJ/K, the reaction is spontaneous below a certain temperature. Calculate that temperature.
5.) Draw two voltaic cells: one with positive voltage, and one with negative voltage. Label all parts of each.