CHEM126 – CHAPTER 18 – BASIC HOMEWORK / ELECTROCHEMISTRY II

 

CHAPTER 18 BASIC HOMEWORK:

ELECTROCHEMISTRY II

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Question 1

 

Check those statements that are correct.

Explanation of standard reduction potentials

 

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Explanation

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Question 2

 

What is the voltage for the reaction under standard conditions: 2Al(s) + 3Pb2+(aq) → 2Al3+(aq) + 3Pb(s)?
Oxidation and reduction reactions
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Explanation

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Question 3

 

Check the statement which are correct.
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Explanation

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Question 4

 

What is the voltage for the reaction under standard conditions: 3Ag(s) + Cr3+(aq) → 3Ag+(aq) +Cr(s)? (See above for reduction potentials.)

Standard conditions mean any amount of the solids (as long as there is some), solutions are 1 M, and gases are 1 atm.

 

 

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Explanation

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Question 5

 

Check the statement which are correct.
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Explanation

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Question 6

 

What is the voltage under standard conditons for the reaction: 2Ag(s) + I2(s) → 2Ag+(aq) + 2I-(aq)?
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Explanation

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Question 7

 

Which or the following statements are true about a spontaneous oxidation-reduction reaction?
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Explanation

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Question 8

 

Find ΔGo in J for: Al3+(aq) + 3e- → Al(s) Eo = -1.66 V
Relation between free energy and voltage

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Explanation

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Question 9

 

Find ΔG in J for: X4+(aq) + 4e- → X(s) E = -1.62 V
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Explanation

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Question 10

 

Which statement is INCORRECT for the following exothermic reaction?

Cu2+(aq) +Zn(s) → Cu(s) + Zn2+(aq)

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Explanation

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Question 11

 

Which of the following statements is NOT correct about the Galvanic cell shown below?

A battery has a voltage and produces a current (flow of electrons) in a circuit. The voltage and current can be made to do useful work such as running an electric motor. A galvanic cell generates electricity like a battery.

 

Select one:

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Explanation

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Question 12

 

In the Zn-Cu galvanic cell shown above, which of the following statements are true?
Anode and Cathode defined
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Explanation

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Question 13

 

What is the standard voltage or cell potential of a Cr-Hg cell? (Remember to switch one-half reaction to oxidation and to balance the number of electrons–use paper.)

Cr3+(aq)+ 3e- → Cr(s) Eo = -0.74 V
Hg2+(aq)+ 2e- → Hg(l) Eo = +0.789 V

Calculating Voltage

 

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Explanation

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Question 14

 

For the above galvanic cell which statments are correct?
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Explanation

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Question 15

 

For the reaction given below the [H+] is increased from 1.00 M to 3.00 M. What happens to the voltage? Write i for increases, n for no change, and d for decreases.

LeChatelier’s Principle

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Explanation

Increasing the reactant concentration above the stantard concentration increases the driving force or voltage to reduce the stress of more reactant.

Question 16

 

For the above reaction what happens to the voltage if a larger zinc electrode is used? Write i for increases, n for no change, and d for decreases.

Solids and Equilibrium/ Voltage

 

 

Explanation

Recall, that the amount of a solid or pure liquid has no effect on equilibrium. A larger zinc electrode does increase the maximum current because there is more surface area for the oxidation of the zinc.

Question 17

 

For the above reaction the [Zn2+] is decreased from 1.00 M to 0.30 M. What happens to the voltage?

 

 

Explanation

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Question 18

 

For the above reaction the H2 pressure is increased from 1.00 atm to 4.2 atm. What happens to the voltage?

 

 

Explanation

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Question 19

 

For the above reaction the Cl- concentration is increased from 1.00 M to 4.50 M by the addition of NaCl. What happens to the voltage?

 

 

Explanation

The overall reaction has nothing to do with the chloride ion concentration.

Question 20

 

For the Zn-H2 cell, what is the voltage if [Zn2+] = 6.67 M, [H+] = 0.0194 M, and the hydrogen pressure is 18.0 atm.

The Nernst Equation

 

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Explanation

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Question 21

 

What is n (the number of moles of electrons) transferred for the following oxidation/ reduction reaction?

2Al(s) + 6H+(aq) → 2Al3+(aq) + 3H2(g)

Determining Electrons Transferred

 

 

 

Explanation

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Question 22

 

2Al(s) + 6H+(aq) → 2Al3+(aq) + 3H2(g)

For the above Al-H2 cell, what is the voltage if [Al3+] = 5.0561 M, [H+] = 5.3 M, and the hydrogen pressure is 0.0856 atm. Eo = 1.66 V.

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Explanation

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Question 23

 

In the galvanic cell below, where the process is sponataneous, on which electode is the metal deposited and what is the metal?

 

 

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Explanation

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Question 24

 

In electrolysis a power supply is required to drive the reaction in the opposite direction to which it wants to go.

In the above example of electrolysis, on which electode is the metal deposited and what is the metal?
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Explanation

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Question 25

 

In the reduction of zinc ions to zinc:

Zn2+(aq) + 2e- → Zn(s)

how many moles of electrons are needed to produce 1 mole of zinc?

 

 

Explanation

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Question 26

 

If a current of 4.96 A flows for 15.32 hr, then what quantity of charge (in C) has flowed?

Current definition and calculation

 

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Explanation

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Question 27

 

In the reduction of aluminum ions to alumimum: Al3+(aq) + 3e- → Al(s)

how many moles of alumimun are produced by 0.76 moles of electrons?chem126-18bii - Fluff Butt Reviews

 

 

Explanation

Hint, 3 moles of electrons produce 1 mole of aluminum.

Question 28

 

If a current of 8.70 A flows for 18.03 hr, then how many moles of electrons have flowed?
The Faraday constant
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Explanation

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Question 29

 

In the reduction of aluminum ions to alumimum: Al3+(aq) + 3e- → Al(s)

how many grams of alumimun are produced by a current of 1.81 A for 7.63 hr?
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Explanation

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