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Unit 10: the Mole & Chemical Composition

Total questions: 33

Worksheet time: 4hrs 51mins

Name
Class
Date
1.

How many molecules are in 2.5 mol of NaCl?

a)

1.50 x1024 molecules

b)

1.50 molecules

c)

4.15 molecules

d)

1.51 x1024 molecules

2.

How many moles are in 3.01 x 1022 atoms of magnesium?

a)

0.05 moles

b)

1.81 x 1046 moles

c)

5.00 x 1021 moles

d)

5.00 moles

3.

How many grams are in 1.2 x 1024 atoms of C?

a)

29.34 grams

b)

23.94 grams

c)

6.02 grams

d)

1.21 grams

4.

What is the percent composition by mass of sulfur (S) in the compound MgSO4?

a)

20.22%

b)

19.85%

c)

26.64%

d)

28.64%

5.
Calculate the number of atoms in 0.0340 g Zn.
a)
5.200 x 10-4 atoms Zn
b)
3.130 x 1023 atoms Zn
c)
3.130 x 1020 atoms Zn
d)
1 atom Zn
6.
Which pair has the same empirical formula?
a)
NaCrO4 and Na2Cr2O7
b)
C2H4O2 and C6H12O6
c)
C3H6O3 and C2H6O2
d)
CH4 and C2H6
7.
What is the molar mass of PbSO4
a)
303.3 g/mol
b)
294.7g/mol
c)
163.8g/mol
d)
372g/mol
8.

N3O3 can be classified as which type of formula?

a)

Empirical

b)

Molecular

c)

Both

9.

Which formula is an empirical formula?

a)

H2O2

b)

C2H6O12

c)

CaCl2

d)

N2O8

10.
What is the percent by mass of sodium in NaCl?
a)
39%
b)
61%
c)
35%
d)
65%
11.
What are the units for molar mass?
a)
grams
b)
amu
c)
grams/mole
d)
liters
12.
Fluorine is diatomic.  What is the molar mass of fluorine gas?
a)
18.998 g/mol
b)
37.996 g/mol
c)
9 g/mol
d)
18 g/mol
13.

*What is the molar mass of B2(CO3)3?

a)

81.6 g/mol

b)

94.8 g/mol

c)

38.8 g/mol

d)

201.6 g/mol

14.
A formula that shows the smallest whole-number ratio of the elements of a compound.
a)
molecular formula
b)
molar mass
c)
mole
d)
empirical formula
15.

*Find the percent composition of N2S2.

a)

N: 69.6% S: 30.4%

b)

N:36% S: 75.6%

c)

N: 96.6% S: 3.4%

d)

N: 30.4% S: 69.6%

16.

*You are given the following percentages: 40.05% S and 59.95% O. Find the empirical formula for these elements. (keep two decimal places throughout calculations)

a)

SO

b)

SO2

c)

SO3

d)

SO4

17.

*What is the empirical formula if you have 88.80% copper and 11.20% oxygen?

a)

Cu3O8

b)

CuO4

c)

Cu2O

d)

Cu4O10

18.

*What is the total number of atoms contained in 80 grams of neon?

a)

6.02 x 1023

b)

1.2 x 1024

c)

2.4 x 1024

d)

4.8 x 1024

19.

The empirical formula of a compound is CH2O, and it's molecular mass is 120 grams/molecule. Calculate its molecular formula.

a)

C3H6O3

b)

C4H8O4

c)

C2H4O2

d)

CH2O

20.

The molecular formula for a carbon and hydrogen compound is C8H18. What is the empirical formula?

a)

C8H18

b)

C9H4

c)

C18H8

d)

C4H9

21.

Chalk is mostly made of calcium carbonate, CaCO3. If it took 48.6 g of chalk to write your name on the sidewalk, how many moles of calcium carbonate does your name contain?

a)

0.486 mol

b)

0.714 mol

c)

1.40 mol

d)

2.06 mol

22.
What is the definition for Avogadro's number?
a)
number of grams per one mole of a substance
b)
whole number ratio that is a multiple of a chemical formula
c)
simplest, whole number ratio of a chemical formula
d)
6.02 x 10^23 particles per one mole of a substance
23.
Which would have more atoms?
a)
1 mole of Li
b)
1 mole of Au
c)
1 mole of Si
d)
None, all are equal
24.
How many steps are in a gram to mole conversion?
a)
1
b)
2
c)
3
d)
4
25.
What is the molar mass of one molecule of Nitrogen N2?
a)
14.01 amu
b)
14.01 g
c)
28.02 g
d)
28.02 amu
26.
What is the molecular formula if the empirical formula is C2H5 and the molecular molar mass is 58.14 g/mol?
a)
C2H5
b)
C4H10
c)
C1H2.5
d)
C4H8
27.
Which expression below show the correct method of determining the percent composition of Sodium in Na2CO3?
a)
%Na = (22.99g/106g) x 100
b)
%Na = (22.99g/106) / 100
c)
%Na = (45.98g/106g) x 100
d)
%Na = (106/45.98g) x 100
28.
Which of the following dimensional analysis setups will correctly convert 27.76g of Li to atoms of Li?
a)
A
b)
B
c)
C
d)
D
29.
Which of the following dimensional analysis setups will correctly convert 2.50 moles of sodium to grams of sodium?
a)
A
b)
B
c)
C
d)
D
30.
Which of the following dimensional analysis setups will correctly convert 4.00x1023atoms of cobalt to moles of cobalt? How many moles of colbalt are there?
a)
setup B : 0.6644mol Co
b)
setup A: 2.41x1047mol Co
c)
setup A : 0.664mol Co
d)
setup B: 2.41x1047mol Co
31.

How many Liters are in 25 g O2

a)

73.5 L

b)

17.5 L

c)

35.0 L

d)

17.9 L

32.

Convert 2.17 L H2 to grams H2.

a)

0.049 g

b)

0.098 g

c)

24.1 g

d)

0.195 g

33.

Convert 25 L N2 to moles of N2.

a)

2.22 moles

b)

560 moles

c)

1.11 moles

d)

6.72 moles

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