AP CHEM - UNIT 9

Which of the following statements is true concerning the reaction shown above?

Oxygen is both oxidized and reduced.

What is the standard cell potential of galvanic cell Z?

0.78 V

According to the standard reduction potentials given above, which of the following mathematical operations correctly calculates the standard cell potential for the reaction represented below?

(+1.66 V) + (+0.80 V) = +2.46 V

In a certain experiment, molten CaCl2 undergoes electrolysis, and the electrical current is 12.0 amps. Which of the following calculations is set up correctly to determine the time (in seconds) required to produce 1.00 gram of calcium?

(2)(96485)/(40.08)(12.0)

A certain reaction is thermodynamically favored at temperatures below 400.K, but it is not favored at temperatures above 400. K. The value of ΔHo for the reaction is -20 kJ/mol. What is the value of ΔSo for the reaction? (Assume that ΔHo and ΔSo do not change with temperature.)

-50 J mol-1 K-1

Which of the following reactions is not thermodynamically favored at low temperatures but becomes favored as the temperature increases?

2 H2O(g)->2 H2(g) + O2(g) 484 90.0

At 25oC, the equilibrium constant for the reaction represented above has a value of 1.3. At 50oC, the value of the equilibrium constant is less than 1.3. Based on this information, which of the following must be correct?

At 25ºC, ΔHº for the reaction is negative.

Based on the information in the table above, which of the following reactions is favored to occur under standard conditions?

Cl2(g) + Fe(s) → 2Cl-(aq) + Fe2+(aq)

A direct current is passed through a 1.00 M aqueous solution of lithium chloride (LiCl). Chlorine gas is observed as a product at the anode. Based on the information in the table above, which of the following identifies the chemical species that is formed at the cathode and gives the correct justification?

H2(g) is produced at the cathode because | -0.83 | is less than | -3.05 |.

The reaction represented above goes essentially to completion. What can be inferred about ΔSº for the reaction at 298 K?

It must be positive because ΔGº is negative and ΔHº is positive.

Which of the following processes involves the greatest increase in entropy?

MgSO3(s) -> MgO(s) + SO2(g)

Which of the following statements is true concerning the two reactions shown above?

N2 is oxidized in Reaction #2, and reduced in Reaction #1.

For which of the following processes does the value of ΔS decrease (ΔS < 0) ?

Precipitation of silver chloride

In galvanic cells Y and Z, which of the following takes place in half-cell 3?

Reduction occurs in cell Y, and oxidation occurs in cell Z.

For the reaction represented above, ΔGo has a value of -2.9 kJ/mol, which indicates that the reaction is thermodynamically favored. However, diamond is a stable substance that does not show any evidence of conversion into graphite at 298 K and 1 atm. Which of the following best accounts for this observation?

The activation energy for the reaction is very large.

It is observed that the reaction shown above goes essentially to completion. Which of the following is a true statement about the thermodynamic favorability of the reaction?

The reaction is favorable and driven by an enthalpy change only.

If the half-cell containing 1.00 M Fe(NO3)2(aq) in galvanic cells Y and Z is replaced with a half-cell containing 5.00 M Fe(NO3)2(aq), what will be the effect on the cell voltage of the two galvanic cells?

The voltage will increase in cell Y and decrease in cell Z.

When the voltaic cell shown above is operated under standard conditions, the initial concentrations of Cu2+(aq) and Ag+(aq) are each equal to 1.0 M. The cell potential is equal to 0.46 V at 25oC. A few drops of concentrated hydrochloric acid, HCl(aq), are added to the beaker containing the cathode, and a precipitate forms. Which of the following correctly predicts the effect of this change on the cell potential and gives the correct justification for it?

cell potential less than 0.46 V [Ag+] has decreased

A standard voltaic cell is to be constructed using two different metals. Based on the standard reduction potentials listed in the table above, which combination will produce the largest cell potential?

silver and zinc

Under which of the following conditions will an exothermic reaction be thermodynamically favorable?

when ∆S is positive

The equilibrium constant for the reaction above is 4*10^15. Which of the following correctly describes the standard voltage (Eo) and the standard free energy change (ΔGo) for this reaction?

ΔGº <0 and Eº >0

Which of the following is true for the process represented above at 327oC and 1 atm? The normal melting point of Pb is 327oC.

ΔH = TΔS

The reaction above is thermodynamically favorable at 25oC. What are the signs of ΔHo, ΔSo, and ΔGo ?

∆H = - ∆S = - ∆G = -