CHE 107 - HOUR EXAMINATION II - 20 October 1994

University of Kentucky - Department of Chemistry


1. Calculate the pH of a solution after 10.0 mL of 0.100 M NaOH is added to 40.0 mL of 0.250 M HBr.

A. 0.18 B. 0.74 C. 1.00 D. 13.00


2. How many mL of a 0.200 M solution of H2SO4 is required to titrate 40.0 mL of a 0.300 M solution of NaOH to the equivalence point?

A. 30.0 mL B. 40.0 mL C. 26.7 mL D. 60.0 mL


3. The pH at the equivalence point in the titration of 0.10 M NH3 with 0.10 M HCl will correspond to a solution that is

A. neutral. B. slightly acidic. C. slightly basic. D. strongly basic.


4. Which one of the following solutions would be a buffer solution?

A. HCl(aq) + NaCl(aq) B. CH3COOH(aq)(acetic acid) + NH3(aq) C. HF(aq) + B(OH)3(aq) D. NaH2PO4(aq) + Na2HPO4(aq)


5. What is the [H+] of a solution that is 0.100 M in formic acid, HCOOH, and 0.100 M in sodium formate, HCOONa? Ka for HCOOH = 1.8 x 10-4.

A. 1.8 x 10-7 B. 1.8 x 10-4 C. 1.8 x 10-5 D. 1.8 x 10-3


6. A buffer was prepared by mixing 0.60 moles of HF and 0.40 moles of NaF in enough water to make a 1.00 L solution. Calculate the pH of this solution. Ka for HF = 3.5 x 10-4.

A. 3.28 B. 3.46 C. 3.64 D. 3.82


7. Phenolphthalein is a colorless weak acid whose conjugate base is pink. If phenolphthalein changes color in the pH range 8.3-10.0, which of the following values is the Ka for phenolphthalein?

A. 1.0 x 10-7 B. 2.0 x 10-9 C. 5.0 x 10-6 D. 3.5 x 10-5


8. Which one of the following statements is true with regard to a 0.10 M H2SO4 solution?

A. [H2SO4] > [H+] B. [H+] = [SO42-] C. [SO42-] > [HSO4-] D. [H+] > [HSO4-]


9. The Ka values for sulfurous acid, H2SO3, are

Ka1 = 1.7 x 10-2 and Ka2 = 6.4 x 10-8.

What is the Kb value for the sulfite ion, SO32-?

A. 6.4 x 10-8 B. 1.6 x 10-7 C. 1.7 x 10-2 D. 5.9 x 10-13


10. Consider the triprotic acid H3PO4 with Ka values of

Ka1 = 7.5 x 10-3, Ka2 = 6.2 x 10-8, and Ka3 = 2.2 x 10-13.

Which one of the following statements is false?

A. A solution of H3PO4 is acidic. B. A solution of NaH2PO4 is acidic. C. A solution of Na2HPO4 is neutral. D. A solution of Na3PO4 is basic.


11. Which one of the following is not amphoteric?

A. HCO3- B. Al(OH)3 C. HSO3- D. Ca(OH)2


12. Of the salts KCN, PbI2, ZnS and MgCl2, which ones would be significantly more soluble in acidic solution than in pure water?

A. KCN and ZnS B. KCN and PbI2 C. PbI2 and MgCl2 D. MgCl2 and ZnS


13. The mathematical form of the first law of thermodynamics is

A. w = -P delta V B. PV = nRT C. delta G = delta H - T delta S D. delta E = q + w


14. How much P-V work is done when 0.500 mol of Na(s) reacts with H2O(l) at 298 K and 1.00 atm? (The molar volume of a gas under these conditions is 24.4 L). The chemical reaction is:

2 Na(s) + 2 H2O(l) = H2(g) + 2 NaOH(aq)

A. 24.4 L-atm B. 12.2 L-atm C. 6.10 L-atm D. 48.8 L-atm


15. Which one of the following is in its standard state?

A. C(graphite) B. C(g) C. C60(s) D. C(diamond)


16. Which one of the following is a formation reaction? (That is, for which one is delta Hrxno = delta Hfo ?)

A. S(s) + O3(g) = SO3(g) B. O3(g) = 3 O(g) C. N2(g) + 2 H2(g) = N2H4(g) D. 1/2 O2(g) + H2O(g) = H2O2(l)


17. Calculate delta Hrxno for

2 H2S(g) + 3 O2(g) = 2 H2O(l) + 2 SO2(g)

delta Hfo kJ/mol H2O(l) -286 H2O(g) -242 SO2(g) -297 H2S(g) -21

A. -562 kJ B. -1014 kJ C. -1124 kJ D. Insufficient data to calculate delta Hrxno.


18. The heats of formation of four different compounds with the formula C4H8 are given below. All burn in air according to the equation

C4H8 + 6 O2 = 4 CO2 + 4 H2O

Which one would make the best fuel? (or, which one gives the most negative delta Hrxn?)

A. 1.17 kJ/mol B. -5.70 kJ/mol C. -10.06 kJ/mol D. -13.99 kJ/mol


19. When a liquid is vaporized

A. delta S = 0. B. delta H = 0. C. delta H < 0. D. delta S > 0.


20. Arrange the following in order of increasing entropy, So, values:

Ba(s), CH4(g), C3H8(g), Mg(s)

A. CH4, C3H8, Mg, Ba B. Ba, CH4, C3H8, Mg C. Mg, Ba, CH4, C3H8 D. C3H8, Ba, CH4, Mg


21. For which of the following reactions is delta S the most negative?

A. PCl5(g) = PCl3(g) + Cl2(g) B. NH3(g) + HCl(g) = NH4Cl(s) C. CaO(s) + H2O(l) = Ca(OH)2(aq) D. Ag2S(s) + O2(g) = 2 Ag(s) + SO2(g)


22. If the following reaction, in which a bond is broken, is spontaneous at 1600 C
Br2(g) = 2 Br(g)

the following must be true.

A. delta H is positive and delta S is positive for the reaction. B. delta G is negative for all temperatures. C. delta H is negative and delta S is negative for the reaction. D. delta H is negative and delta S is positive for the reaction.


23. For CH3OH(methanol), delta Gvapo = 4.34 kJ/mol at 298 K; the vaporization reaction is

CH3OH(l) = CH3OH(g)

What is the equilibrium vapor pressure of CH3OH at 298 K?

A. 0.998 atm = 759 Torr B. 5.76 atm = 4381 Torr C. 0.17 atm = 132 Torr D. 6.6 x 10-4 atm = 0.5 Torr


24. Kp = 9.4 x 10-5 for the reaction

N2(g) + 3 H2(g) = 2 NH3(g)

at 427oC. Calculate the value of delta Go at 427oC.

A. +33 kJ B. -33 kJ C. -54 kJ D. +54 kJ


25. Which of the following is not a state function?

A. qp = delta H B. w C. q + w = delta E D. delta G - delta H = T delta S


1 February 1996