Question 1

A 50.00 mL sample of 0.150 M formic acid (Ka = $$1.8 	imes 10$$^{-4}$$) is titrated with 0.150 M NaOH. What is the pH at the equivalence point?

Accepted Answer

pH = 8.81

Question 2

Which of the following changes will increase the entropy ($$S) of a $$system?

Accepted Answer

Phase change from solid to liquid

Question 3

Given the reaction $$C(s) + O_2$(g) \rightarrow CO_2$(g)$$ and the standard molar entropies $$S^\circ(C) = 2 J/$$mol K, $$S^\circ(O_2$) = 205 J/$$mol K, $$S^\circ(CO_2$) = 213.74 J/$$mol K, what is $$\Delta S_{rxn}$$?

Accepted Answer

$$\Delta S_{rxn} = +6.74 J/$$mol K

Question 4

Which atom is being reduced in the reaction: $$Sb + $$HNO_3$$ \rightarrow Sb_2O_3 + NO + H_2O$$?

Accepted Answer

N

Question 5

What is the oxidation number of Xe in $$XeF_4$$?

Accepted Answer

+4

Question 6

A 35.00 mL sample of a weak acid (HA) is titrated with 0.150 M NaOH. The equivalence point occurs at 42.60 mL of NaOH. What is the initial concentration of the weak acid?

Accepted Answer

0.183 M

Question 7

Which of the following has the lowest entropy?

Accepted Answer

C(s)

Question 8

Calculate the change in entropy for 1 mole of Hg during melting at $$-37.9^\circC$$. $$\Delta H_{fus}(Hg) = 2.33 kJ/$$mol.

Accepted Answer

$$\Delta S = 9.90 J/K$$

Question 9

Which of the following best describes a spontaneous process?

Accepted Answer

A process that occurs without outside intervention

Question 10

Given $$\Delta H_{rxn} = -92 kJ/$$mol and $$\Delta S_{rxn} = -0.199 kJ/$$mol K, at what temperature (in K) does $$\Delta G_{rxn} = 0$$?

Accepted Answer

462 K

Question 11

Which of the following is true about the anode in a voltaic cell?

Accepted Answer

It is where oxidation occurs

Question 12

What is the cell potential for a voltaic cell constructed from the following half-reactions? 
Co$$^{2+} + 2e$^-$$ → Co ($$E^\circ = -0.28 V) 
Au$^{3+} + 3e$^-$$ → Au ($$E^\circ = 1.50 V)$$

Accepted Answer

1.78 V

Question 13

Which of the following is the correct balanced redox reaction for: 
Au$$^{3+}(aq) + I$^-(aq$$) → Au(s) + I$$_2(s$$)?

Accepted Answer

2Au$$^{3+}(aq) + 6I$^-(aq$$) → 2Au(s) + 3I$$_2(s)$$

Question 14

A 40.00 mL solution of 0.200 M methylamine (Kb = $$4.4 	imes 10$$^{-4}$$) is titrated with 0.200 M HCl. What is the pH after 20.00 mL HCl is added?

Accepted Answer

pH = 10.64

Question 15

Which of the following is the correct relationship between Gibbs free energy and the equilibrium constant $$K at $$temperature $$T$$?

Accepted Answer

$$\Delta G^\circ = -RT \ln K$$

Question 16

Which atom is being oxidized in the reaction: $$C + H_2SO_4 \rightarrow CO_2$ + SO_2$ + H_2O$$?

Accepted Answer

C

Question 17

Calculate the standard free energy ($$\Delta G^\circ) $$for a cell with $$E^\circ_{cell} = 1.78 V $$and $$n = 6$$ electrons transferred. ($$F = 96,485 C/$$mol)

Accepted Answer

$$-1030.46 kJ/$$mol

Question 18

A battery powers a device at 1 mA for 3,000 hours. How many grams of Co are consumed? ($$F = 96,485 C/$$mol, MW(Co) = 58.9 g/mol, 2 mol e$$^-$$ per mol Co)

Accepted Answer

3.30 g

Question 19

Which of the following has the highest entropy?

Accepted Answer

C(s)

Exam 3 Review: Thermochemistry, Electrochemistry, and Titrations

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