Chp 8--Exam 4

What energy change is associated with the reaction to obtain one mole of H2 from one mole of water vapor? The balanced equation is 2 H2O(g) → 2H2(g) + O2(g) and the relevant bond energies are: H — H = 436 kJ/mol; H — O = 467 kJ/mol; O — O = 146 kJ/mol; O O = 498 kJ/mol.

+249 kJ

For the compound FeCl3, what is the oxidation state of Fe?

3+

In this electrochemical cell, the reduction half-reaction is

Cu2+ (aq) + 2e− → Cu (s)

Which type of widely used battery is not rechargeable?

Zinc-manganese alkaline

Which is an oxidation half-reaction?

Zn → Zn2+ + 2e−

Chemical energy is converted directly into electrical energy in

a galvanic cell.

Which of the following next-generation batteries would be good choices based on the future availability of its elements?

Al-ion

What moves in the salt bridge from the cathode to the anode?

Anions

How do the interactions that are broken in water when it is boiled compare with those broken when water is electrolyzed?

Boiling water breaks intermolecular attractions and electrolysis breaks covalent bonds

What is the anode in a typical Li-ion battery composed of?

Graphite

Why is it so expensive to ship hydrogen as a liquid as is often done with other gas?

Hydrogen has to be shipped at a very low temperature

How does the reaction of hydrogen and oxygen to produce energy in a fuel cell differ from their interaction during the direct combustion of hydrogen and oxygen? I. The direct combustion of hydrogen and oxygen produces several different products, whereas the fuel cell produces only water II. Much less heat energy is produced in a fuel cell than via direct combustion of hydrogen and oxygen III. The fuel cell is more useful for producing electricity than direct combustion.IV. It is much easier to control the hydrogen and oxygen during direct combustion than during their reaction in a fuel cell

I, II, and III only

A NiCd battery uses nickel and cadmium to produce a potential difference. Using these equations, answer the below question. I. 2NiO(OH)(s) + 2H2O(l) + 2e− → 2Ni(OH)2(s) + 2OH−(aq) II. Cd(s) + 2OH−(aq) → Cd(OH)2(s) + 2e− III. Cd(s) + 2NiO(OH)(s) + 2H2O(l) → 2Ni(OH)2(s) + Cd(OH)2(s)

II

Which is not an advantage of using a solid electrolyte in a fuel cell?

It eliminates the need for an oxidant; only a fuel is required

What is the purpose of the hot KOH solution in the fuel cell?

It maintains electroneutrality by working as an electrolyte; allowing transfer of ions between the half cells where the hydrogen and oxygen react

Which is not a necessary consideration for a battery designed to run a cell phone or portable MP3 player?

It must use liquid, aqueous solutions

Which type of battery is widely used to store the excess energy generated by windmill farms and solar panels?

Lead-acid

Which has not been suggested as a reasonably practical way to store large amounts of hydrogen in relatively small spaces for its use as a fuel?

Liquefy hydrogen under pressure and store it much as we do with liquefied natural gas today

What condition must be met for a battery to be rechargeable?

The electrochemical reaction of the battery must be reversible

Why can the lead-acid batteries used in cars generate electricity for several years before running down?

The mechanical motion of the engine drives an alternator that generates electricity to recharge the battery

What is the primary determinant of the voltage developed by a battery?

The nature of the materials in the reaction

Which is the cathode in this galvanic cell?

The solid silver electrode

Consider Ohm's Law. Which of the following are correct? Question 26 options: A)Voltage is proportional to current B)Voltage is inversely proportional to current C)Current and resistance are proportional to each other D)All of these choices are correct

Voltage is proportional to current

At present, it will be difficult and perhaps inappropriate to develop an economy based on burning hydrogen rather than natural gas or gasoline because

although hydrogen is abundant, pure hydrogen is not found naturally on earth. Hydrogen is difficult or expensive to isolate and collect.

A major advantage of a fuel cell over a standard battery is that

as long as oxygen and fuel are supplied, a fuel cell will not run down like a battery will.

Batteries must be used in addition to solar cells when generating household electricity because

batteries must store and then supply the energy when sunlight is not available.

As fuel cells become more widely accepted and are used more, we will

be able to generate electricity in places where we cannot now do so.

In general, a modern hybrid vehicle is less polluting than a standard vehicle because it runs on both a

gasoline engine and an electric motor run by a rechargeable battery.

During the chemical reaction in an electrochemical cell,

oxidation occurs at the anode.

Electrolysis is a process that

requires an electrical current to decompose water into hydrogen gas and oxygen gas.