Download - cK-12

Changes in Oxidation Number in Redox Reactions Quiz
1. What happens to the oxidation number of an element that is oxidized in a reaction?
a) Its oxidation number increases.
b) Its oxidation number decreases.
c) Its oxidation number changes from positive to negative.
d) Its oxidation number may increase or decrease.
2. What happens to the oxidation number of an element that is reduced in a reaction?
a) Its oxidation number increases.
b) Its oxidation number decreases.
c) Its oxidation number changes from negative to positive.
d) Its oxidation number may increase or decrease.
3. Only ionic reactions result in the increase or decrease of oxidation numbers.
a) True
b) False
4. Consider the reaction below that produces ethane gas from ethene.
C2 H4 (g) + H2 (g)  C2 H6 (g)
The ethene gas (C2H4) is being:
a) reduced because of the addition of hydrogen.
b) reduced because the oxidation number of the carbon atom is decreasing.
c) oxidized because the oxidation number of the carbon atom is increasing.
d) both a and b
1
Questions 5-7: Given the reaction below:
3Mg(s) + N2 (g)  Mg3 N2 (s)
5. The oxidation number of Mg changes from _____, meaning that the Mg is being _____.
a) 0 to −3; oxidized
b) 0 to −3; reduced
c) 0 to +2; oxidized
d) 0 to +2; reduced
6. The oxidation number of N changes from _____, meaning that the N is being _____.
a) 0 to −3; oxidized
b) 0 to −3; reduced
c) 0 to +2; oxidized
d) 0 to +2; reduced
7. Identify the oxidizing agent and the reducing agent in the reaction.
8. Given the reaction for the combustion of methanol.
2CH3OH(l) + 3O2 (g)  2CO2 (g) + 4H2O(l)
What element is being oxidized and what element is being reduced? What are the
oxidation number changes for those elements?
Questions 9 and 10: Given the reaction below between copper metal and nitric acid.
3Cu(s) + 8HNO3 (aq)  3Cu(NO3 )2 (aq) + 2NO(g) + 4H2O(l)
9. What element is being oxidized and what element is being reduced? What are the
oxidation number changes for those elements?
2
10. What is the oxidizing agent in the reaction?
a) Cu
b) HNO3
c) Cu(NO3)2
d) NO
3