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Empirical Formula and Percent Composition

Total questions: 62

Worksheet time: 2hrs 34mins

Name
Class
Date
1.
Which pair has the same empirical formula?
a)
NaCrO4 and Na2Cr2O7
b)
C2H4O2 and C6H12O6
c)
C3H6O3 and C2H6O2
d)
CH4 and C2H6
2.
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
3.
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
4.
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
5.
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
6.
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 
7.
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
8.
Whats the empirical formula of a molecule containing 18.7% of Lithium, 16.3% of Carbon and 65.0% of oxygen?
a)
CO2Li3
b)
Li2CO3
c)
Li3CO2
d)
LiCO5
9.
What is the percent by mass of oxygen in MgO?
a)
20%
b)
40%
c)
50%
d)
60%
10.
What is the percent by mass of sodium in NaCl?
a)
39%
b)
61%
c)
35%
d)
65%
11.
What is the percent by mass of fluorine in CaF2 (gram-formula mass = 78 g/mol)?
a)
24%
b)
49%
c)
51%
d)
65%
12.
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
13.
A chemical formula that shows the actual # and kinds of atoms present in one molecule of a compound is called_________
a)
ionic formula
b)
covalent formula
c)
empirical formula
d)
molecular formula
14.
Which pair has the same empirical formula?
a)
NaCrO4 and Na2Cr2O7
b)
C2H4O2 and C6H12O6
c)
C3H6O3 and C2H6O2
d)
CH4 and C2H6
15.
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)
16.
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)
17.

Do the diagrams have the same molecular formula?

a)

Yes

b)

No

18.

Do the diagrams have the same empirical formula?

a)

Yes

b)

No

19.

If black ball represents carbon (C) atom and white balls represent hydrogen (H) atoms. What is the molecular formula of the diagram shown?

a)

CH

b)

CH4

c)

C4H

d)

C4H4

20.

If black ball represents carbon (C) atom and white balls represent hydrogen (H) atoms. What is the molecular formula of the diagram shown?

a)

CH

b)

CH4

c)

C2H4

d)

C4H4

21.

Do the diagrams have the same molecular formula?

a)

Yes

b)

No

22.

Do the diagrams have the same empirical formula?

a)

Yes

b)

No

23.

The molecular and empirical formula of a compound are __________ the same.

a)

always

b)

sometimes

c)

never

d)

one and

24.

Chloroform, a toxic substance that may cause severe liver, kidney, and heart damage, has the percent composition by mass of this compound is 10.06% carbon, 0.84% hydrogen, and 89.09% chlorine. What is the empirical formula of this compound?

a)

C3H3Cl

b)

CH6Cl3

c)

CH3Cl3 

d)

CHCl3

25.

Chloroform, a toxic substance that may cause severe liver, kidney, and heart damage, has the percent composition by mass of this compound is 10.06% carbon, 0.84% hydrogen, and 89.09% chlorine. What is its molar mass in g/mol?

a)

124.42

b)

121.39

c)

119.37 

d)

74.51

26.

Chloroform, a toxic substance that may cause severe liver, kidney, and heart damage, has the percent composition by mass of this compound is 10.06% carbon, 0.84% hydrogen, and 89.09% chlorine. If a compound which shares the same empirical formula as chloroform is known to have a molar mass of 223.53g/mol, what is the compound’s mole ratio with chloroform?

a)

2

b)

3

c)

4

d)

5

27.

If a compound has an empirical formula of CH2 and a gram formula mass of 42 g/mol , what is its molecular formula?

(keep in mind that masses have been rounded to nearest whole number for simplicity)

a)

CH4

b)

C3H4

c)

C2H4

d)

C3H6

e)

CH2

28.

If a compound has an empirical formula of NO2 and a gram formula mass of 92 g/mol , what is its molecular formula?

(keep in mind that masses have been rounded to nearest whole number for simplicity)

a)

N2O4

b)

NO2

c)

N3O6

d)

N2O3

e)

N2O2

29.

What is the percent composition of Hydrogen in CH4CH_4  ? Below is the Percent Composition formula from your Reference Tables adapted to this particular situation...

% comp =Mass contribution from the specific elementTotal mass in formula x 100\%\ comp\ =\frac{Mass\ contribution\ from\ the\ specific\ element}{Total\ mass\ in\ formula}\ x\ 100  

a)

80 %

b)

4.04 %

c)

0.25 %

d)

25.17 %

e)

74.83 %

30.

How many moles are present in 38.91 grams of LiF?

a)

1.0 moles

b)

2.0 moles

c)

0.5 moles

d)

1.5 moles

31.

What is the gram formula mass of calcium nitrate, Ca(NO3)2?

(answer choices rounded to nearest whole number)

a)

148g

b)

164g

c)

102g

d)

70g

32.

Calculate how many grams are in 0.700 moles of H2O2

a)

23.81 grams

b)

34.02 grams

c)

48.65 grams

d)

28.02

33.

What is the percent composition of nitrogen in NH3 nitrogen trihydride (otherwise known as ammonia)?

Below is the Percent Composition formula from your Reference Tables adapted to this particular situation...

% comp =Mass contribution from the specific elementTotal mass in formula x 100\%\ comp\ =\frac{Mass\ contribution\ from\ the\ specific\ element}{Total\ mass\ in\ formula}\ x\ 100  

a)

21.26 %

b)

462 %

c)

25 %

d)

82.22 %

e)

17.78 %

34.

What is the gram formula mass of carbon dioxide, CO2?

(answer choices rounded to nearest whole number)

a)

28.01 g/mol

b)

44.01 g/mol

c)

117.86 g/mol

d)

56.02 g/mol

35.

What is the Molarity of a solution created by dissolving 116.88 grams of NaCl in water to a final volume of 500 mL?

a)

234 M

b)

1.00 M

c)

4.00 M

d)

0.234 M

36.

How many grams are needed to make 250 mL of a 2.00 M NaCl solution?

a)

500 g

b)

466 g

c)

29.2 g

d)

8.55 g

37.
What is the percent composition by mass of oxygen in the compound MgSO4 (gram formula mass = 120 g/mol)?
a)
20%
b)
27%
c)
46%
d)
53%
38.
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
39.
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
40.
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
41.
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 
42.
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
43.
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
44.
Which of the following is considered an empirical formula?
a)
CH3COOH
b)
C6H12O6
c)
H2O
45.
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
46.
Which pair has the same empirical formula?
a)
NaCrO4 and Na2Cr2O7
b)
C2H4O2 and C6H12O6
c)
C3H6O3 and C2H6O2
d)
CH4 and C2H6
47.
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
48.
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
49.
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
50.

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

51.
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
52.

Which one is the empirical formula?

C4H6

a)

CH

b)

CH3

c)

C2H3

d)

C4H6

53.

Which of the following compounds contains the most oxygen by mass?

a)

H2O

b)

H2O2

c)

H3O+

d)

none because they have equal percentage composition 

54.

Which between carbon monoxide and carbon dioxide has a greater carbon content by mass?

a)

carbon monoxide

b)

carbon dioxide

c)

none because they have equal percentage composition 

d)

cannot be determined 

55.

The molar mass of this compound is computed to be 74.14g/mol. 

Identify this alcohol.

a)

ethanol (C2H6O)

b)

propanol (C3H8O)

c)

butanol (C4H10O) 

d)

pentanol (C5H12O)

56.

An unlabeled bottle of alcohol produces the following composition: 

C = 59.94% H = 13.44% O = 26.62%.

Which alcohol was analyzed?

a)

ethanol (C2H6O)

b)

propanol (C3H8O)

c)

butanol (C4H10O) 

d)

pentanol (C5H12O)

57.

The A compound with a molar mass of 92.16g/mol is known to have the same empirical formula as this alcohol. Which alcohol is being described?

a)

ethanol (C2H6O)

b)

propanol (C3H8O)

c)

butanol (C4H10O) 

d)

pentanol (C5H12O)

58.

Prof. X wanted the alcohol that has the highest oxygen content. Which alcohol should you give him?

a)

ethanol (C2H6O)

b)

propanol (C3H8O)

c)

butanol (C4H10O) 

d)

pentanol (C5H12O)

59.

Arrange the elements of this common herbicide, C₉H₉ClO₃,  according to increasing percent composition.

a)

Cl<O<H<C 

b)

H<O<Cl<C

c)

H<Cl<O<C

d)

Cl<H<O<C

60.

The mass of each element per 100 mass unit of compound is called __________.

a)

percent composition

b)

molar mass

c)

mole ratio

d)

molecular formula

61.

Glycerol has a chemical formula of CxH8O3 and has a molar mass of 92.09g/mol. 

How many carbons does glycerol have?

a)

1

b)

2

c)

3

d)

4

62.

Glycerol has a chemical formula of CxH8O3 and has a molar mass of 92.09g/mol. 

What percent of glycerol is carbon?

a)

66.66%

b)

39.10%

c)

21.42%

d)

3.25%

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