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# Understanding Thermodynamics and Electrochemistry

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1. If the equilibrium constant for a two-electron redox reaction at 298 is 1.0×10−4, calculate the corresponding and under standard conditions.

2. A cell has a standard emf of 0.104 at 298 . What is the value of the equilibrium constant for the cell reaction if ?

3. A voltaic cell utilizes the following reaction: What is the emf of this cell under standard conditions? What is the emf of this cell when 1.9 , 1.8×10−2 , 0.44 and the of the solution in the cathode compartment is 2.7?

4Fe2+ (aq) + O2 (g) + 4H+ (aq)  4Fe3+ (aq) + 2H2C

4. A voltaic cell is constructed with two silver-silver chloride electrodes, each of which is based on the following half-reaction:
.
The two cell compartments have 1.42×10−2 and 3.00 , respectively.

A. What is the cell emf for the concentrations given?
B. For the anode compartment, predict whether will increase, decrease, or stay the same as the cell operates.
C. For the cathode compartment, predict whether will increase, decrease, or stay the same as the cell operates.

5. During a period of discharge of a lead-acid battery, 375 of from the anode is converted into . What mass of is reduced at the cathode during this same period?

6. This oxidation-reduction reaction in acidic solution is spontaneous:
A solution containing and is poured into one beaker, and a solution of is poured into another. A salt bridge is used to join the beakers. A platinum foil is placed in each solution, and the two solutions are connected by a wire that passes through a voltmeter. Calculate the emf of the cell at 298 when the concentrations are the following: 0.40, 0.11 , 1.80 , 2.7×10−4 , 1×10−3 .

Thermodynamics

1. How much heat is produced in burning 2 of under standard conditions if both reactants and products are brought to 298 ?

2. What is the maximum amount of useful work that can be accomplished under standard conditions by this reaction when 2 of is burned?

3. How much heat is produced in burning 8 of ethylene under standard conditions if reactants and products are brought to 298 and is formed?

4. Consider the decomposition of barium carbonate:

A. Calculate the equilibrium pressure of at 298 .

5. The for methylamine at 25 is .

A. What is the chemical equation for the equilibrium that corresponds to Kb?
B. By using the value of , calculate for the equilibrium in part A.
C. What is the value of at equilibrium?

The potassium-ion concentration in blood plasma is about , whereas the concentration in muscle-cell fluid is much greater . The plasma and intracellular fluid are separated by the cell membrane, which we assume is permeable only to .

6. What is for the transfer of 10 of from blood plasma to the cellular fluid at body temperature (37 )?

7. What is the minimum amount of work that must be used to transfer this ?

The reaction is the basis of a suggested method for removal of from power-plant stack gases. The standard free energy of each substance are = 0 , = -228.57 , = -300.4 , = -33.01 .

8. What is the equilibrium constant for the reaction at 298 ?

9. If = and the vapor pressure of water is 20 , calculate the equilibrium pressure in the system at 298 .

10. Would you expect the process to be more or less effective at higher temperatures?