Question 1

Which of the following best describes a redox reaction?

Accepted Answer

A reaction that involves the transfer of electrons between reactants.

Question 2

In the half-reaction $\mathrm{Mn^{2+} (aq) \rightarrow MnO_4^- (aq)}$, what is the change in oxidation state for manganese?

Accepted Answer

$+2$ to $+7$

Question 3

When balancing redox reactions, what is the purpose of multiplying the half-reactions by appropriate coefficients?

Accepted Answer

To ensure the number of electrons lost equals the number gained.

Question 4

Which species is oxidized in the reaction $\mathrm{Fe^{2+} (aq) + Cr (s) \rightarrow Fe (s) + Cr^{3+} (aq)}$?

Accepted Answer

$\mathrm{Cr}$

Question 5

In the reaction $\mathrm{Cl_2 (aq) + KI (aq) \rightarrow KCl (aq) + I_2 (aq)}$, which element is reduced?

Accepted Answer

Chlorine

Question 6

What is the correct balanced half-reaction for the reduction of $\mathrm{Co^{3+}}$ to $\mathrm{Co^{2+}}$?

Accepted Answer

$\mathrm{Co^{3+} (aq) + e^- \rightarrow Co^{2+} (aq)}$

Question 7

In the reaction $\mathrm{Ce^{4+} (aq) + Sn^{2+} (aq) \rightarrow Ce^{3+} (aq) + Sn^{4+} (aq)}$, which species acts as the reducing agent?

Accepted Answer

$\mathrm{Sn^{2+}}$

Question 8

Which step is necessary to balance the overall charge in a redox reaction?

Accepted Answer

Add electrons to the more negative side of each half-reaction.

Question 9

Given the half-reactions: $\mathrm{Fe^{2+} (aq) \rightarrow Fe (s) + 2e^-}$ and $\mathrm{Cr (s) \rightarrow Cr^{3+} (aq) + 3e^-}$, what is the least common multiple of electrons to balance the redox reaction?

Accepted Answer

$6$

Question 10

Which of the following is the correct balanced overall redox reaction for $\mathrm{Fe^{2+} (aq) + Cr (s) \rightarrow Fe (s) + Cr^{3+} (aq)}$?

Accepted Answer

$3Fe^{2+} (aq) + 2Cr (s) \rightarrow 3Fe (s) + 2Cr^{3+} (aq)$

Question 11

In the reaction $\mathrm{Cl_2 (aq) + 2KI (aq) \rightarrow 2KCl (aq) + I_2 (aq)}$, what is the oxidation state change for iodine?

Accepted Answer

$-1$ to $0$

Question 12

Which of the following is a correct step in balancing redox reactions in acidic solution?

Accepted Answer

Add $\mathrm{H^+}$ ions to balance hydrogen.

Question 13

In the half-reaction $\mathrm{Cl_2 (aq) \rightarrow 2Cl^- (aq)}$, how many electrons are gained or lost?

Accepted Answer

2 electrons gained

Question 14

Which of the following statements about half-reactions is correct?

Accepted Answer

Half-reactions are used to identify oxidation and reduction processes separately.

Question 15

In the reaction $\mathrm{Ce^{4+} (aq) + Sn^{2+} (aq) \rightarrow Ce^{3+} (aq) + Sn^{4+} (aq)}$, what is the total number of electrons transferred?

Accepted Answer

2 electrons

Question 16

Which of the following is the correct balanced half-reaction for the oxidation of $\mathrm{Sn^{2+}}$ to $\mathrm{Sn^{4+}}$?

Accepted Answer

$\mathrm{Sn^{2+} (aq) \rightarrow Sn^{4+} (aq) + 2e^-}$

Question 17

What is the correct order of steps for balancing a redox reaction using the half-reaction method?

Accepted Answer

Break into half-reactions, balance electrons, multiply to equalize electrons, combine and cancel electrons.

Question 18

In the reaction $\mathrm{Ni (s) + Co^{3+} (aq) \rightarrow Ni^{2+} (aq) + Co^{2+} (aq)}$, which element is reduced?

Accepted Answer

Cobalt

Question 19

Which of the following is a real-world application of redox reactions?

Accepted Answer

Photosynthesis in plants

Balancing Redox Reactions: Concepts and Practice for GOB Chemistry

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