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Quiz: Empirical and Molecular Formulas

Total questions: 25

Worksheet time: 47mins

Name
Class
Date
1.

A compound is found to contain 40.92% carbon, 4.58% hydrogen, and 54.50% oxygen. What is the empirical formula of the compound?

a)

C4H8O2

b)

C3H4O3

c)

C2H4O

d)

CO2H4

2.

If a compound is found to contain 32.37% sodium, 22.58% sulfur, and 45.06% oxygen, what is its empirical formula?

a)

Na2S2O5

b)

Na2S2O3

c)

Na2SO4

d)

NaSO3

3.

A compound is found to contain 70.0% iron and 30.0% oxygen. What is the empirical formula of the compound?

a)

Fe2O3

b)

Fe3O2

c)

FeO

d)

FeO2

4.

If the empirical formula of a compound is CH2O and its molar mass is 90.08 g/mol, what is its molecular formula?

a)

C3H6O3

b)

C2H4O2

c)

C4H8O4

d)

CH4O4

5.

The empirical formula of a compound is CH2 and its molar mass is 84.16 g/mol. What is the molecular formula of the compound?

a)

CH4

b)

C4H8

c)

C6H12

d)

C3H6

6.

A compound has an empirical formula of NO2 and a molar mass of 92.02 g/mol. What is its molecular formula?

a)

N2O2

b)

NO3

c)

N2O4

d)

NO4

7.

What is the percent by mass of oxygen in MgO, (MM= 40.31 g/mol)?

a)
20%
b)
40%
c)
50%
d)
60%
8.
What is the percent by mass of fluorine in CaF2 (gram-formula mass = 78 g/mol)?
a)
24%
b)
49%
c)
51%
d)
65%
9.
Which pair has the same empirical formula?
a)
NaCrO4 and Na2Cr2O7
b)
C2H4O2 and C6H12O6
c)
C3H6Oand C2H6O2
d)
CH4 and C2H6
10.

What is the empirical formula for C4H6?

a)

CH

b)

CH3

c)

C2H3

d)

C4H6

11.

What is the empirical formula for N2S3?

a)

NS

b)

N3S2

c)

N2S3

12.

Which of the following compounds are both an empirical AND molecular formula (check all that apply)

a)

C6H12O6

b)

C12H22O11

c)

H2O2

d)

S2O4

e)

H2O

13.
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
14.

Which of these is NOT an empirical formula?

a)

CH2

b)

C2H5

c)

C6H4

d)

C3H7

e)

C5H17

15.

A compound is found to be 38.7% Chlorine (Cl, 35.45 g/mol) and the rest oxgyen (O, 16.00 g/mol). What is the empirical formula of this compound?

a)

Cl2O7

b)

ClO

c)

Cl2O3

d)

None of these

16.

How many Carbons "C" are in C18H34O3

a)

18

b)

34

c)

3

d)

37

17.
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
18.

How would you calculate the molar mass for C4H6?

a)

12.01 + 1.01

b)

4(12.01) + 6(1.01)

c)

2(12.01) + 3(1.01)

d)

6(12.01) + 4(1.01)

19.

Empirical Formula = CF2

Molecular formula mass = 192 g/mol

Molecular Formula = ?

a)

C4F8

b)

C8F4

c)

C3F6

d)

C2F4

20.

You are given 40.05g S and 59.95g O. Find the empirical formula for these elements.

a)

SO

b)

SO2

c)

SO3

d)

SO4

21.

What is the empirical formula of K2SO4?

a)

K2SO4

b)

KSO2

c)

K2SO2

d)

KSO8

22.

Succinic acid has an empirical formula of C2H3O2 and a molecular weight of 118 grams/mol. What is the molecular formula of succinic acid?

Atomic weights: C = 12.0, H = 1.01, O = 16.0

a)

C6H12O6

b)

C2H3O2

c)

C3H6O3

d)

C4H6O4

23.

A compound has a molar mass of 170.0 g/mol and an empirical formula of SiF3. The compound's molecular formula is:

a)

SiF3

b)

Si5F15

c)

Si2F6

d)

Si4F12

24.

When calculating the empirical formula the mole ratio is given as follows:

H1O3.5

What will the EF be?

a)

H1O3.5

b)

HO3.5

c)

HO4

d)

H2O7

25.

Which of the following molecular formulas is correctly paired with its empirical formula?

a)

C2H2 and CH3CH3

b)

C6H6 and C2H2

c)

P4O10 and P2O5

d)

SO2 and SO3