REDOX Worksheet
1. In which substance is oxidation number of
nitrogen zero?
a.
b.
c.
d.
NH3
N2
NO2
N2O
a.
b.
c.
d.
2. In the reaction Al + Cr3+  Al3+ + Cr, the
reducing agent is?
a.
b.
c.
d.
3. What is the oxidation number of carbon in
NaHCO3?
4. As an S2- ion is oxidised to an S atom, the
number of protons in its nucleus
Al
Cr3+
Al3+
Cr
a.
b.
c.
d.
5. If element X forms the oxides XO and X2O3,
the oxidation numbers of element X are:
a. +1 and +2
c. +1 and +3
b. +2 and +3
d. +2 and +4
6. Oxygen has a positive oxidation number in the
compound:
a. H2O
c. OF2
b. H2O2
d. IO2
+6
+2
-4
+4
Increases
Decreases
Stays the same
Yes
8. Calculate the oxidation number of chromium
in each of the following:
a. Cr2O3
b. Na2Cr2O7
c. CrSO4
7. What is the oxidation number of sulfur in
H2SO4
a. 0
c. +6
b. -2
d. +4
d. CrO42- (chromate ion)
e. Cr2O72- (dichromate ion)
REDOX Worksheet
1. In which substance is oxidation number of
nitrogen zero?
a.
b.
c.
d.
NH3
N2
NO2
N2O
a.
b.
c.
d.
2. In the reaction Al + Cr3+  Al3+ + Cr, the
reducing agent is?
a.
b.
c.
d.
3. What is the oxidation number of carbon in
NaHCO3?
4. As an S2- ion is oxidised to an S atom, the
number of protons in its nucleus
Al
Cr3+
Al3+
Cr
a.
b.
c.
d.
5. If element X forms the oxides XO and X2O3,
the oxidation numbers of element X are:
a. +1 and +2
c. +1 and +3
b. +2 and +3
d. +2 and +4
6. Oxygen has a positive oxidation number in the
compound:
a. H2O
c. OF2
b. H2O2
d. IO2
+6
+2
-4
+4
Increases
Decreases
Stays the same
Yes
8. Calculate the oxidation number of chromium
in each of the following:
a. Cr2O3
b. Na2Cr2O7
c. CrSO4
7. What is the oxidation number of sulfur in
H2SO4
a. 0
c. +6
b. -2
d. +4
d. CrO42- (chromate ion)
e. Cr2O72- (dichromate ion)