Chapter 19 Test

Question 1

Which of the following is the properly balanced equation for the net ionic equation below in acidic solution?
MnO4-(aq) + CN-(aq) -> MnO2(aq) + OCN-(aq)

Answer 1

2H+(aq) + 2MnO4-(aq) + 3CN-(aq) -> 2MnO2(aq) + H2O(l) + 3OCN-(aq)

Question 2

What is the oxidation state of the chromium atom in each of the compounds listed below?

Na2Cr2O7, CrO2, and Cr3+

Answer 2

+6, +4, and +3

Question 3

In the reaction of sodium chlorate and iron(II) sulfate below, which of the following represents the reduction half reaction?
NaClO3(aq) + 8FeSO4(aq) + 4HSO4-(aq) -> NaClO(aq) + 4Fe2(SO4)3(aq) + 2H2O(l)

Answer 3

4e- + ClO3-(aq) -> ClO-(aq)

Question 4

Manganese can be found in many oxidation states. Which of the following is the strongest oxidant?

MnO4−, MnO2, MnCl2, Mn

Answer 4

MnO4−

Question 5

In the diagram of a galvanic cell, which is the cathode?

Answer 5

D

Question 6

Use the standard reduction potentials to calculate the E°cell for the following reaction in an electrolytic cell

Cu2+(aq) + 2Ag(s) -> Cu(s) + 2Ag+(aq)

Answer 6

−0.46 V

Question 7

Calculate the standard Gibbs free energy change in J / mol at 25°C for the following reaction:

Zn2+(aq) + Cu(s) -> Zn(s) + Cu2+(aq)

Based on this ΔG ̊, would you expect Zn2+ ions to plate out on Cu metal?

Answer 7

2.123 * 10^5 J/mol, no

Question 8

Calculate the Ecell for the Cl2/Cl- electrode for 25°C, given these values:

PCl2 = 12.0 atm           [Cl-] = 1.25*10^-3M
Cl2(g) = 2e- -> 2Cl-(aq)            E° = +1.36V

Answer 8

+1.56 V

Question 9

Which equation best describes the solubility of AgCl?

Answer 9

Ksp = e^(nFE°cell/RT)

Question 10

Which of the following has the highest energy-to-mass ratio?

Answer 10

lithium battery

Question 11

The transfer of electrons from iron to oxygen and water is all that is necessary for the formation of rust.

Answer 11

false

Question 12

Given the following standard reduction potentials, which of the following would not be a good choice as a sacrificial anode for iron?

Answer 12

nickel

Question 13

How many milligrams of copper metal would be produced in 24 hours of electroplating of a copper(II) ion solution with 9.0 A of current?
Faraday’s constant is 96,485 coulombs per mole of electrons
1 A = 1 C/s

Answer 13

260,000 mg Cu

Question 14

A strip of copper is placed in a beaker with a 1.0 M solution of Cu(NO3 )2. A strip of silver is placed in a second beaker with A 1.0 M solution of AgNO3. A salt bridge connects the two beakers and the two metal electrodes are connected by wires to a digital voltmeter. The voltmeter reads 0.46 V. Which reaction is occurring at the anode and which reaction is occurring at the cathode? Note: In this cell, the standard reduction potential for Ag | Ag+ is + 0.80 V and the standard reduction potential for Cu | Cu2+ is + 0.34 V.

Answer 14

Anode Reaction: Cu -> Cu2+ + 2e-

Cathode Reaction: Ag+ + e- -> Ag

Question 15

What is the chemical formula for rust?

Answer 15

Fe2O3 • H2O

Question 16

Where does reduction occur in an electrolytic cell?

Answer 16

Cathode

Question 17

Why is zinc used in batteries?

Answer 17

It is a good reducing agent

Question 18

What is a volt?

Answer 18

joule per coulomb

Question 19

What is reduction in a redox reaction?

Answer 19

A gain of electrons

Question 20

What is the pH of a solution used in the following galvanic cell with a potential (Ecell ) of −0.365 V at 25°C?

Ni(s)|Ni2+ (0.1M)||H + (?)|H2(1 atm)

R • T / F = 0.0592 at 25°C

Answer 20

10.5

Question 21

Which of the following is a disadvantage of a lead-acid storage battery?

Answer 21

it has a low energy-to-mass ratio

Question 22

Mercury dry cell batteries are very stable because all of the phases comprising it are either solid or liquid. Why isn’t the mercury battery more commonly used?

Answer 22

Mercury is a toxic heavy metal and it is not used more often because of the environmental issues.

Question 23

Why must the switch be open to measure EMF?

Answer 23

Because of resistance in the cell

Question 24

What is the balanced equation representing the decomposition of hydrogen peroxide in acidic conditions?
H2O2(aq) –> H2(g) + O2(g)

Answer 24

2H+(aq) + 2H2O2(aq) -> H2(g) + O2(g) + 2H2O(l)

Question 25

The state capitol of Iowa has a gold dome. The mass of gold used in plating the dome is 100 troy ounces (1.00 troy ounce = 31.10 grams). How many days would it take to plate out this quantity of gold from an 1.0 M aqueous solution of AuCl3 using an external current of 7.5 A?

Answer 25

7