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Worksheets

Finding Oxidation Numbers

Total questions: 25

Worksheet time: 19mins

Name
Class
Date
1.

What is the oxidation number of chlorine in KCl?

a)

+1

b)

-1

c)

+5

d)

+7

2.

What is the oxidation number of sulfur in H2SO4H_2SO_4  

a)

0

b)

-2

c)

+2

d)

+6

3.

What is the change in oxidation number for oxygen, when it goes from O2O_2 to MgO?

a)

0 to +2

b)

0 to -2

c)

0 to -1

d)

0 to +1

4.

What is the change in oxidation number for chlorine as it goes from Cl2Cl_2  to Cl-

a)

0 to +1

b)

+1 to 0

c)

0 to -1

d)

-1 to 0

5.

What is the oxidation number of Au(s)?

a)

+1

b)

-1

c)

+2

d)

0

6.

What is the oxidation number of O2(s)?

a)

+1

b)

-1

c)

-2

d)

0

7.

What is the oxidation number of K+?

a)

0

b)

+1

c)

-1

d)

+2

8.

What is the oxidation number of Br-(s)?

a)

0

b)

+1

c)

-1

d)

+3

9.

In which formula does nitrogen have the lowest oxidation number?

a)

N2

b)

HNO2

c)

HNO3

d)

Li3N

10.

In which formula does manganese have the highest oxidation number?

a)

MnO

b)

MnO2

c)

Mn2O3

d)

KMnO4

11.

What is the oxidation number of sulfur in H2SO4?

a)

0

b)

-2

c)

+2

d)

+6

12.

What is the oxidation number of chromium in K2Cr2O7?

a)

0

b)

+2

c)

+3

d)

+6

13.

Which change in oxidation numbers shows a loss of electrons?

a)

0 to -1

b)

-1 to -2

c)

-2 to -1

d)

0 to -2

14.

Which change in oxidation numbers shows a loss of electrons?

a)

0 to -1

b)

0 to +1

c)

+2 to +1

d)

+2 to 0

15.

Which change in oxidation numbers shows the greatest gain in electrons?

a)

0 to -3

b)

+2 to -1

c)

+5 to -3

d)

0 to -2

16.

What is the change in oxidation numbers as K+ goes to K

a)

0 to +1

b)

+1 to 0

c)

+2 to 0

d)

+2 to 0

17.

What is oxidation number of copper in CuO?

a)

0

b)

+1

c)

+2

d)

none of the above

18.

What is the oxidation number of iron in Fe2O3?

a)

0

b)

+2

c)

+3

d)

+1

19.

In which substance does chlorine have the highest oxidation number?

a)

Cl2

b)

KCl

c)

HClO4

d)

NaClO3

20.

What is the oxidation number of hydrogen in NH4+

a)

0

b)

-1

c)

+1

d)

-3

21.

During oxidation, what happens to the oxidation number?

a)

decreases

b)

increases

c)

remains the same

22.

During reduction, what happens to the oxidation number?

a)

decreases

b)

increases

c)

remains the same

23.

What is the oxidation number of phosphorus in H3PO4?

a)

0

b)

+1

c)

+3

d)

+5

24.

In which substance does carbon have the highest oxidation number?

a)

C

b)

CO

c)

CO2

d)

MgC2O4

25.

Which statement is correct in regards to oxidation numbers

a)

Oxygen is always -2

b)

Hydrogen is always +1

c)

Single, uncombined elements are always 0

d)

Group 2 elements will form +1