h11 batteries solutions

villa (rjv436) – H11 - Batteries – mccord – (51175) 1

This print-out should have 10 questions.Multiple-choice questions may continue onthe next column or page – find all choicesbefore answering.

001 (part 1 of 3) 10.0 points

The galvanic cell below uses the standardhalf-cells Mg2+ |Mg and Zn2+ |Zn, and a saltbridge containing KCl(aq). The voltmetergives a positive voltage reading.

− +

A B

voltmeter

D→←C

E F

SaltBridge

Identify A and write the half-reaction thatoccurs in that compartment.

1. Zn(s); Zn(s)→ Zn2+(aq) + 2 e−

2. Mg(s); Mg2+(aq) + 2 e− →Mg(s)

3. Mg(s); Mg(s)→Mg2+(aq) + 2 e− cor-rect

4. Zn(s); Zn2+(aq) + 2 e− → Zn(s)

Explanation:

002 (part 2 of 3) 10.0 pointsWhat happens to the size of the electrode

A during the operation of the cell?

1. decreases correct

2. No change

3. increases

Explanation:

003 (part 3 of 3) 10.0 pointsWhat is the voltmeter reading?

1. +3.40 V

2. +2.50 V

3. +4.30 V

4. +1.60 V correct

5. +0.50 V

Explanation:

004 10.0 pointsWhat condition must be met for a battery tobe rechargeable?

1. Either its anode or its cathode must gen-erate a gas as a result of the electrochemicalreaction.

2. It must generate electricity via an acid-base reaction rather than via an oxidationreduction reaction.

3. The electrochemical reaction of the bat-tery must be reversible. correct

4. The battery must be open to the outsideso that it can vent any internal pressure thatbuilds up from gases within it.

Explanation:Definition

005 10.0 pointsThe discharge for a lead storage battery isindicated by

Pb + PbO2 + 2H2SO4 → 2PbSO4 + 2H2O

What is the highest oxidation state of leadin the species in this equation?

1. two

2. one

3. zero


4. four correct

5. three

Explanation:Consider the oxidation numbers for hydro-

gen and oxygen in the reaction:0 −2 +1 −2 −2 +1−2

Pb+PbO2+2H2SO4→ 2PbSO4+2H2O0 −4 +2 −8 −8 +2−2

Balance the sulfur in the SO2−4

:0 −2 +1+6−2 +6 −2 +1−2

Pb+PbO2+2H2SO4→ 2PbSO4+2H2O0 −4 +2+6−8 +6 −8 +2−2

Balance the lead (Pb):0 +4 −2 +1+6−2 +2+6 −2 +1−2

Pb+PbO2+2H2SO4→ 2PbSO4+2H2O0 +4 −4 +2+6−8 +2+6 −8 +2−2

Looking at lead, the highest oxidation stateis +4 in PbO2.

006 10.0 pointsThe overall reaction for the discharge of anickel/cadmium cell is

Cd + NiO2 + 2H2O→ Cd(OH)2 +Ni(OH)2

Which of the following statements is true?

1. It is impossible to recharge anickel/cadmium cell.

2. Cadmium metal loses 2 electrons and isconverted to Cd2+ at the cathode.

3. The nickel is oxidized during this reac-tion.

4. Insoluble Cd(OH)2 is deposited on theanode. correct

Explanation:Looking at the reaction above,

Cd→ Cd2+ + 2 e−

is an oxidation reaction that will occur at theanode.The nickel is not oxidized because we have

shown that Cd is being oxidized.Nickel/cadmium batteries are rechargable.

Insoluble CD(OH)2 is deposited on the an-ode since Cd is oxidized at the anode.

007 10.0 pointsWhich type of widely used battery is NOTrechargeable?

1. nickel-cadmium (NiCad)

2. lead-acid (storage batteries)

3. alkaline correct

4. lithium-ion

Explanation:Alkaline batteries were not designed to be

rechargeable and do not do so efficiently, al-though there are some websites that disagree.

008 10.0 pointsIn a voltaic cell, electrons flow from the ?to the ? in the external circuit.

1. products; reactants

2. anode; cathode correct

3. reactants; products

4. cathode; anode

Explanation:

009 10.0 pointsA major advantage of lead storage batteries isthat they are

1. lightweight.

2. disposable.

3. rechargeable. correct

4. All of these

Explanation:

010 10.0 pointsVoltaic cells in which the original reactantscan be regenerated by passing a direct current


through the cell are called

1. fuel cells.

2. voltaic dry cells.

3. primary voltaic cells.

4. secondary voltaic cells. correct

5. tertiary voltaic cells.

Explanation:

h11 batteries solutions

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