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Percent Composition

Total questions: 15

Worksheet time: 3hrs 30mins

Name
Class
Date
1.
What is the percent by mass of oxygen in MgO?
a)
20%
b)
40%
c)
50%
d)
60%
2.
What is the percent by mass of magnesium in MgO?
a)
20%
b)
40%
c)
50%
d)
60%
3.
What is the percent by mass of sodium in NaCl?
a)
39%
b)
61%
c)
35%
d)
65%
4.
What is the percent by mass of chlorine in NaCl?
a)
39%
b)
61%
c)
35%
d)
65%
5.
In which compound is the percent composition by mass of Cl equal to 42%?
a)
HClO (gram formula mass = 52 g/mol)
b)
HClO2 (gram formula mass = 68 g/mol)
c)
HClO3 (gram formula mass = 84 g/mol)
d)
HClO4 (gram formula mass = 100 g/mol)
6.

What is the percent composition by mass of oxygen in the compound MgSO4 (total compound mass = 120 g/mol)?

a)
20%
b)
27%
c)
46%
d)
53%
7.

What is the percent composition by mass of magnesium in the compound MgSO4 (total compound mass = 120 g/mol)?

a)
20%
b)
27%
c)
46%
d)
53%
8.

What is the percent composition by mass of sulfur in the compound MgSO4 (total compound mass = 120 g/mol)?

a)
20%
b)
27%
c)
46%
d)
53%
9.

What is the percent by mass of calcium in CaF2 (total compound mass = 78 g/mol)?

a)
24%
b)
49%
c)
51%
d)
65%
10.

What is the percent by mass of fluorine in CaF2 (total compound mass = 78 g/mol)?

a)
24%
b)
49%
c)
51%
d)
65%
11.

Which element has an abundance of 39.03% in the compound sodium phosphate, Na3PO4

a)

Na

b)

P

c)

O

d)

None of the above

12.

Which element in the compound potassium cyanide, KCN, has a percent composition of 60.97%?

a)

K

b)

C

c)

N

d)

None of the above

13.
What is the percent composition of Benzene, C6H6?
a)
C = 50%
H = 50%
b)
C = 85.7 %
H = 14.3%
c)
C = 92.2%
H = 7.8%
d)
C = 71.9%
H = 28.1%
14.
Find the percent composition of Cu2S?
a)
%Cu= 67.987 %S= 32.013
b)
%Cu= 79.854   %S= 20.145
c)
%Cu= 35.946   %S= 64.054
15.

Carbon monoxide, a deadly gas, has a chemical formula of CO (one carbon atom with one oxygen atom). If you look at the total atomic mass of CO, does carbon or oxygen make up more of the mass?

a)

carbon

b)

oxygen

c)

they are exactly the same

d)

it is impossible to tell