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Worksheets

Empirical and Molecular Formula

Total questions: 18

Worksheet time: 29mins

Name
Class
Date
1.
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)
Mg3N
d)
MgN
2.
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
3.
Which pair has the same empirical formula?
a)
NaCrO4 and Na2Cr2O7
b)
C2H4O2 and C6H12O6
c)
C3H6Oand C2H6O2
d)
CH4 and C2H6
4.
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
5.

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.


What is the empirical formula of J?

a)

C4HNO2

b)

CH2N2O

c)

C2HNO2

d)

CHNO

6.
Given the following: 42.07% Na, 18.89% P, and 39.04% O, determine the empirical formula.
a)
 NaPO2
b)
Na2PO3
c)
Na3PO4
d)
NaPO4
7.
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
8.
What is the molecular formula for a compound with the empirical formula: K2SOand a molecular mass of 696g.
a)
K2SO
b)
K8SO16
c)
K8S4O
d)
K8S4O16 
9.

Phenyl magnesium bromide is used as a reagent in organic synthesis. Determine its molecular formula if its molar mass is 181.31 g/mol and it contains 39.75% C, 2.78% H, 13.41% Mg, and 44.07% Br (these are in the correct order).

a)

C12H10Mg2Br2

b)

CHMgBr

c)

C6H5MgBr

d)

C3H2.5MgBr

10.

What is the molecular formula for a compound with the empirical formula: CaCl2 and a molecular mass of 220g.

a)

Ca2Cl4

b)

Ca3Cl6

c)

Ca3Cl9

d)

Ca3Cl5

11.

An unknown compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. It has a molecular mass of 60.0 g/mol. Calculate its molecular formula.

(a)  

12.

A hydrocarbon contains 85.7% carbon with a molecular mass of 84.0 g/mol. Calculate its molecular formula.

(a)  

13.

A piece of iron ore contains 72.3% iron and 27.7% oxygen with a molecular mass of 231.4 g/mol. Calculate its molecular formula.

(a)  

14.

A compound contains 87.4% nitrogen. The remainder is hydrogen. If the molecular mass is 32 g/mol, what is its molecular formula?

(a)  

15.

A compound with a molar mass of 74 g/mol contains 64.8% carbon and 13.5% hydrogen. When it was burned it produced carbon dioxide and water. Calculate its molecular formula.

(a)  

16.

A compound contains 24.8% carbon, 2.0% hydrogen and 73.2% chlorine. It has a molar mass of 96 g/mol. Calculate its molecular formula.

(a)  

17.

An oxide of nitrogen contains 46.7% nitrogen and has a molecular mass of 60 g/mol. What's its molecular formula?

(a)  

18.

A gas sample contained the elements carbon, hydrogen, oxygen, phosphorus and fluorine in the respective quantities: 39.10%, 7.67%, 26.11%, 16.82% and 10.30%. It has a molecular mass of 184 g/mol. What is the molecular formula for this compound?

(a)