Practice Redox Reaction in Chemistry

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

A chemical reaction in which electrons are transferred from one substance (the reducing agent, which is oxidized) to another (the oxidizing agent, which is reduced).

One thing loses electrons (oxidized), another gains them (reduced).

Showing a random 20 of 50 problems.

Example 1

easy
In Cl2+2e−→2Cl−\text{Cl}_2 + 2e^- \rightarrow 2\text{Cl}^-, is chlorine oxidized or reduced?

Example 2

easy
What is the oxidation number of a free element such as NaNa metal?

Example 3

easy
In a redox reaction, the oxidizing agent is the species that does what to electrons?

Example 4

medium
Find the oxidation state of Mn in KMnO4\text{KMnO}_4.

Example 5

medium
Is CaCO3→CaO+CO2\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2 a redox reaction?

Example 6

hard
In a galvanic cell with overall reaction Zn+Cu2+→Zn2++Cu\text{Zn} + \text{Cu}^{2+} \rightarrow \text{Zn}^{2+} + \text{Cu}, identify the species reduced and the cathode material.

Example 7

medium
In 2Fe3++Sn2+→2Fe2++Sn4+2Fe^{3+} + Sn^{2+} \rightarrow 2Fe^{2+} + Sn^{4+}, how many electrons does tin lose?

Example 8

medium
What is the oxidation number of nitrogen in HNO3HNO_3?

Example 9

medium
In Cu+2Ag+→Cu2++2Ag\text{Cu} + 2\text{Ag}^+ \rightarrow \text{Cu}^{2+} + 2\text{Ag}, how many electrons are transferred per Cu atom?

Example 10

hard
In NaH\text{NaH}, what is the oxidation state of hydrogen?

Example 11

medium
Determine whether the following reaction is a redox reaction: HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l)\text{HCl(aq)} + \text{NaOH(aq)} \rightarrow \text{NaCl(aq)} + \text{H}_2\text{O(l)}. Justify your answer.

Example 12

easy
Define a redox reaction and explain the relationship between oxidation and reduction.

Example 13

easy
In 2Na+Cl2→2NaCl2\text{Na} + \text{Cl}_2 \rightarrow 2\text{NaCl}, which species is the reducing agent?

Example 14

medium
Is the disproportionation Cl2→Cl−+ClO−Cl_2 \rightarrow Cl^- + ClO^- a redox reaction?

Example 15

easy
What is the oxidation number of oxygen in most compounds such as H2OH_2O?

Example 16

medium
In MnO4−→Mn2+MnO_4^- \rightarrow Mn^{2+}, what is the change in oxidation number of Mn?

Example 17

easy
OIL RIG: what does 'OIL' stand for?

Example 18

medium
Balance the reduction half-reaction O2→O2−O_2 \rightarrow O^{2-} for the oxide ion.

Example 19

medium
At which electrode does oxidation occur in a galvanic cell?

Example 20

challenge
In 3Cu+8HNO3→3Cu(NO3)2+2NO+4H2O3Cu + 8HNO_3 \rightarrow 3Cu(NO_3)_2 + 2NO + 4H_2O, how many electrons are transferred total?
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