Q: Which of the following reactions is an example of a redox reaction that occurs in a hydrogen fuel cell?

$$2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$$

Question 1

Which of the following best describes the process occurring at the cathode in a typical electrochemical cell?

Accepted Answer

Reduction occurs, and electrons are gained by the species at the cathode.

Question 2

Which of the following reactions is an example of a redox reaction that occurs in a hydrogen fuel cell?

Accepted Answer

$$2	ext{H}_2 + 	ext{O}_2 ightarrow 2	ext{H}_2	ext{O}$$

Question 3

Which statement correctly identifies the oxidising and reducing agents in the reaction $$2	ext{Na} + 	ext{Cl}_2 ightarrow 2	ext{NaCl}$$?

Accepted Answer

Na is the reducing agent and Cl$$_2 is $$the oxidising agent.

Question 4

Which of the following best explains why oxidation and reduction always occur together in a redox reaction?

Accepted Answer

Because the number of electrons lost by one species must equal the number gained by another.

Question 5

What is the oxidation number of sulfur in $$	ext{K}_2	ext{SO}_4$$?

Accepted Answer

$$+6$$

Question 6

Which of the following statements about oxidation numbers is TRUE?

Accepted Answer

Oxidation numbers can be fractional in some compounds.

Question 7

In the reaction $$	ext{CH}_4 + 2	ext{O}_2 ightarrow 	ext{CO}_2 + 2	ext{H}_2	ext{O}$$, which element is oxidised?

Accepted Answer

Carbon

Question 8

A glucose monitor is an example of which application of electrochemistry?

Accepted Answer

Chemical analysis in medical testing

Question 9

Which of the following best describes the change in oxidation number for hydrogen in the reaction $$2	ext{H}_2 + 	ext{O}_2 ightarrow 2	ext{H}_2	ext{O}$$?

Accepted Answer

Hydrogen changes from 0 to +1

Question 10

Which of the following is the correct oxidation number for phosphorus in $$	ext{Mg}_3	ext{P}_2$$?

Accepted Answer

$$-3$$

Question 11

Which of the following is a correct statement about the role of an oxidising agent in a redox reaction?

Accepted Answer

It removes electrons from another substance and is reduced.

Question 12

In the compound $$	ext{NaN}_3$$, what is the oxidation number of nitrogen?

Accepted Answer

$$-1/3$$

Question 13

Which of the following best describes the process of corrosion, such as the rusting of iron?

Accepted Answer

A redox reaction where iron is oxidised and oxygen is reduced.

Question 14

Which of the following is the correct oxidation number for fluorine in $$	ext{KF}$$?

Accepted Answer

$$-1$$

Question 15

Which of the following best describes the change in oxidation number for oxygen in the formation of water from hydrogen and oxygen?

Accepted Answer

Oxygen changes from 0 to -2

Question 16

Which of the following is a correct application of the rules for assigning oxidation numbers?

Accepted Answer

Oxygen usually has an oxidation number of -2, except in peroxides.

Question 17

Which of the following best describes what happens during the electrolysis of molten sodium chloride ($$	ext{NaCl}$$)?

Accepted Answer

Sodium ions are reduced to sodium metal at the cathode.

Question 18

Which of the following is the correct way to write the oxidation number for iron in iron(III) oxide?

Accepted Answer

Fe(III)

Question 19

Which of the following best describes the relationship between oxidation number and redox reactions?

Accepted Answer

Oxidation is an increase in oxidation number; reduction is a decrease.

Question 20

A student is asked to identify whether the reaction $$4	ext{Fe} + 3	ext{O}_2 ightarrow 2	ext{Fe}_2	ext{O}_3 is a $$redox reaction. Which of the following is the best justification?

Accepted Answer

Yes, because the oxidation number of Fe increases from 0 to +3 and O decreases from 0 to -2.

Introduction to Electrochemistry: Redox Reactions and Oxidation Numbers

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