WorksheetsPercent Composition & Empirical/Molecular Formula
Total questions: 15
Worksheet time: 1hrs 11mins
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 calcium in CaF2 (gram-formula mass = 78 g/mol)?
a)
24%
b)
49%
c)
51%
d)
65%
3.
What percentage of the total atomic mass of lithium phosphide (Li3P) is composed of phosphorus?
a)
13%
b)
29%
c)
40%
d)
60%
4.
What is the percent composition of Benzene, C6H6?
a)
C = 50%
H = 50%
H = 50%
b)
C = 85.7 %
H = 14.3%
H = 14.3%
c)
C = 92.2%
H = 7.8%
H = 7.8%
d)
C = 71.9%
H = 28.1%
H = 28.1%
5.
The mass % of aluminum in aluminum sulfate Al2(SO4)3 is:
a)
12.93%
b)
45.70%
c)
7.89%
d)
35.94%
e)
15.77%
6.
A compound consists of 72.2% magnesium(Mg) and 27.8% nitrogen(N) by mass. What is the empirical formula?
a)
Mg4N3
b)
MgN2
c)
Mg3N2
d)
MgN
7.
Which of the following is considered an empirical formula?
a)
CH3COOH
b)
C6H12O6
c)
H2O
8.
You are given the following percentages: 40.05% S and 59.95% O. Find the empirical formula for these elements.
a)
SO
b)
SO2
c)
SO3
d)
SO4
9.
A formula with the lowest whole # ratio of elements in a compound is called
a)
Molecular Formula
b)
Chemical Formula
c)
Empirical Formula
d)
Distance Formula
10.
Glycerol has a molar mass of 92.09g/mol. Its percent composition is: 39.12% C, 8.75% H, and 51.12% O. What is the molecular formula for glycerol?
a)
C2H3O2
b)
CH2O
c)
C2H4O2
d)
C3H8O3
11.
2.40 g of an explosive, J, contains 0.473 g of nitrogen. J also contains 33.8% carbon and 1.41% hydrogen by mass. The remainder of J is oxygen. First, find the percentage by mass of nitrogen using the masses given at the start of the problem. Second, add up the masses of nitrogen, carbon, and hydrogen. Subtract it from 100 to find the percent of oxygen. Then solve for empirical formula using those pervcentages like normal.
What is the empirical formula of J?
a)
C4HNO2
b)
CH2N2O
c)
C2HNO2
d)
CHNO
12.
C25H45
a)
C25H45
b)
CH
c)
C5H9
d)
C9H5
13.
Si2F6
a)
SiF
b)
Si2F6
c)
SiF3
d)
Si6F2
14.
What is the molecular formula if the empirical formula is CH2O and the molecular molar mass is 180.18?
a)
CH2O
b)
C2H4O2
c)
C4H8O4
d)
C6H12O6
15.
What is the molecular formula for a compound with the empirical formula: K2SO4 and a molecular mass of 696g.
a)
K2SO4
b)
K8SO16
c)
K8S4O8
d)
K8S4O16
100 %
