Highlander Help

CHAPTER 18 BASIC HOMEWORK:

ELECTROCHEMISTRY II

Resources:

Have you found videos, websites, or explanations that helped you understand this chapter? Let us know and we'll add them to "Resources" part of this page for other students to use.


 

Question 1

Check those statements that are correct. 

Select one or more:
 Correct
 Correct

 

    

 

Question 2

What is the voltage for the reaction under standard conditions: 2Al(s) + 3Pb2+(aq) → 2Al3+(aq) + 3Pb(s)?
Correct

 

Explanation

2Al(s) +  → 2Al3+(aq)  + 6e-   Ea= -1.66

 3Pb2+(aq) + 6e-→  3Pb(s)     Ec=-0.13

Ecell = Ec-Ea

=-0.13-(-1.66)

=1.53


 

Question 3

Check the statement which are correct.

Select one or more:
 Correct
 Correct

 

    

    

 

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.


Correct

 

Explanation

3Ag(s) → 3Ag+(aq) + 3e-     Ea= 0.8

3e- + Cr3+(aq) →  Cr(s)        Ec=-0.13

Ecell = Ec - Ea

=-0.73-0.8

=-1.53

 

Question 5

Check the statement which are correct.

Select one or more:
 Correct
 Correct

 

    

    

 

Question 6

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

Correct

 

Explanation

2Ag(s) → 2Ag+(aq) + 2e-   Ea=0.80

 I2(s) + 2e-→  2I-(aq)   Ec=0.54


Ecell= Ec-Ea

=0.54-0.8

=-0.26

 

Question 7

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

Select one or more:
 Correct
 Correct

 

    

    

 

Question 8

Find ΔGo in J for: Al3+(aq) + 3e- → Al(s) Eo = -1.66 V

Correct

 

Explanation

ΔG=-nFE

=-3(96500)(-1.66)

=480,570

 

Question 9

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

Correct

 

Explanation

ΔG=-nFE

=-5(96500)(0.46)

=-221,950

 

Question 10

Which statement is INCORRECT for the following exothermic reaction?

Cu2+(aq) +Zn(s) → Cu(s) + Zn2+(aq)

Select one:
 Correct

 

Explanation

Cu2+(aq) + 2e-→ Cu(s)   Ec =-0.34

Zn(s) → 2e- + Zn2+(aq)  Ea=-0.76

Ecell= Ec-Ea

-0.34-(-0.76)

=1.1

 

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:

 Correct

 

    

    

 

Question 12

In the Zn-Cu galvanic cell shown above, which of the following statements are true?
Select one or more:
 Correct
 Correct
 Correct

 

    

    

 

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

Correct

 

Explanation

Ecell=Ec-Ea

=0.789-(-0.74)

=1.529

 

Question 14

For the above galvanic cell which statments are correct?

Select one or more:
 Correct
 Correct
 Correct

 

    

    

 

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

Answer: Correct

 

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.

 

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

Your content goes here...

 

Question 18

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

 

    

    

 

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

Correct

 

Explanation

Ecell=Ecell - 0.0592*log Q/n

Q=(6.67)(18)/(0.0194^2)=319003

=0.76-(0.0592)*log(319003)/2

=0.597

 

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

2Al(s) → 2Al3+(aq) + 6e-

6e- + 6H+(aq) →  3H2(g)

 

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. 

Correct

 

Explanation

Ecell=Ecell - 0.0592*log Q/n

Q= (0.0856)^3*(5.0561)^2/(5.3)^6= 0.000000723

=1.66- (0.0592)*log(0.000000723)/6

=1.72

 

Question 23

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


Select one or more:
 Correct
 Correct

 

    

    

 

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?

Select one or more:
 Correct
 Correct

 

    

    

 

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?

 

    

    

 

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

Correct

 

Explanation

4.96A = 4.96 C/s * 15.32 hr *3600 sec/hr=273553.92

 

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?
Correct

 

Explanation

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


.76e-*1 Al/3mol e-= 0.25333

 

Question 28

If a current of 8.70 A flows for 18.03 hr, then how many moles of electrons have flowed?
Correct

 

Explanation

8.70 A = 8.70 C/s * 18.03 hr * 3600 sec/hr =564699.6 * 1 mol/96500C= 5.85

 

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?

Correct

 

Explanation

1.81 C/s * 7.63 hr * 3600 sec/hr=49717.08*1 mol/96500=0.515203* 1mol Al/3e- = 0.1717 mol Al * 26.98 g/ 1mol Al = 4.633 g


Comments