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Moles, Molar Mass, and Mass percent of compounds

Total questions: 10

Worksheet time: 6mins

Name
Class
Date
1.

Calculate the number of iron atoms in a 4.48 mole sample of iron

a)

2.70 × 1024 Fe atoms

b)

5.70 × 1024 Fe atoms

c)

2.90 × 104 Fe atoms

d)

1.30 × 1034 Fe atoms

2.

A silicon chip used in an integrated circuit of a microcomputer has a mass of 5.68 mg. How many silicon (Si) atoms are present in the chip?

Convert mg to g : 5.68 mg X 10 -3

a)

2.02 X 10 -4 atoms

b)

1.22 X 10-7 atoms

c)

2.23 X 1022 atoms

d)

1.22 X 1020 atoms

3.

A sample of element silver (Ag) has a mass of 21.46 g. how many moles of silver are in sample? How many atoms of silver are in sample?

a)

2.198 X 1020 atoms

b)

0.1989 atoms

c)

1.198 X 1023 atoms

d)

1.178 X 1021 atoms

4.

What is the weight of 7.81 X 10 ²² atoms of Calcium?

a)

5.19 g Co

b)

4.19 g Co

c)

12.14 g Co

d)

7.10 g Co

5.

Cobalt (Co) is a metal that is added to steel to improve its resistance to corrosion. Calculate the number of moles in a sample of cobalt containing 5.00 X 1020 atoms

a)

1.33 X 10 -12 mole

b)

7.30 X 10 -2 mole

c)

8.30 X 10 -4 mole

d)

2.34 X 10 -3 mole

6.

Calculate the molar mass of potassium dichromate K₂Cr₂O₇

a)

354.30 g/mole

b)

294.20 g/mole

c)

221.30 g/mole

d)

122.20 g/mole

7.

What are the molecular weights of H₃PO₄

a)

88.00 grams

b)

91.00 grams

c)

98.00 grams

d)

92.00 grams

8.

What are the molecular weights of Mn₂Se₇

a)

662.60 grams

b)

682.30 grams

c)

622.30 grams

d)

662.60 grams

9.

What are the molecular weights of (NH₄)₂ SO₄

a)

120.11 grams

b)

132.17 grams

c)

112.16 grams

d)

113.19 grams

10.

Mass percent of iron in iron(III) oxide, (Fe2O3)

a)

89.68 %

b)

44.36 %

c)

78.69 %

d)

69.94 %