Free Printable Unit 4.2-4.3 Review (Molar Mass and Chemical Composition)

1.

How many atoms are there in a 0.500 mole sample of helium atoms? (hint: 1 mole = 6.022 x 10²³ particles)

a)

3.01 atoms

b)

3.01 x 10²³ atoms

c)

2.00 atoms

d)

1.20 x 10²⁴ atoms

2.

Approximately how many moles is a 1.82 x 10²⁴ molecule sample of water molecules?

a)

About 3 moles

b)

About 1/3 of a mole

c)

About 2 moles

d)

About 1 mole

3.

What is the molar mass of aluminum oxide, Al₂O₃? (Molar masses: Al = 26.98 g/mol, O = 16.00 g/mol)

a)

112.94 g/mol

b)

101.96 g/mol

c)

2592 g/mol

d)

42.98 g/mol

4.

How many grams would there be in a 2.00 mole sample of NaCl? (Molar mass of NaCl = 58.44 g/mol)

a)

29.2 grams

b)

117 grams

c)

58.4 grams

d)

3.52 x 10²⁵ grams

5.

Determine how many moles an 8.25 g sample of NaCl contains (rounded to correct amount of sig figs). Molar mass of NaCl = 58.44 g/mol

a)

1.41 moles

b)

0.141 moles

c)

7.08 moles

d)

482 moles

6.

What is the correct setup to determine how many molecules of water are in a 2.00 g sample of pure H2O? (molar mass of H2O is 18.02 g/mol)

a)

$2.00\ g\ x\ \frac{1\ mol}{18.02\ g}\ x\ \frac{6.022\ x\ 10^{23}molecules}{1\ mol}\ =\$

b)

$2.00\ g\ x\ \frac{18.02\ g}{1\ mol}\ x\ \frac{1\ mol}{6.022\ x\ 10^{23}molecules}\ =\$

c)

$6.022\ x\ 10^{23}\ molecules\ x\ \frac{1\ mol}{2.00\ g}x\ \frac{18.02\ g}{1\ mol}\ =$

d)

$18.02\ g\ x\ \frac{1\ mol}{1\ gram}x\ \frac{6.022\ x\ 10^{23}\ molecules}{1\ mol}\ =\$

7.

How many liters will 0.250 moles of an ideal gas occupy at STP? (Hint: 1 mole of any ideal gas at STP = 22.4 L)

a)

89.6 L

b)

5.60 L

c)

0.0112 L

d)

0.560 L

8.

How many moles of N₂ gas would occupy 40.0 L of space? (1 mole of gas = 22.4 L at STP)

a)

12,544 moles

b)

1.79 moles

c)

0.560 moles

d)

32.0 moles

9.

What is the percent mass composition of each element in CO₂? Molar masses: C = 12.01 g/mol, O = 16.00 g/mol

a)

50 % C and 50 % O

b)

27.29 % C and 72.71 % O

c)

27.29 % C and 36.35 % O

d)

33.33 % C and 66.67 % O

10.

H₂O is 11.2% H and 88.8 % O by mass. In a 25.0 gram pure sample of H₂O, how many grams is coming from just H atoms?

a)

2.80 grams H

b)

22.2 grams H

c)

12.5 grams H

d)

8.33 grams H

11.

What is the empirical formula for the molecule dodecene, C₁₂H₂₄?

a)

C₆H₁₂

b)

C₃H₆

c)

CH₂

d)

C₄H₈

12.

If the empirical formula for a compound is CH₃ and the molar mass of the compound is 45.12 g/mol, what is the molecular formula for the compound? (molar masses: C = 12.01 g/mol, H = 1.01 g/mol)

a)

C₆H₁₈

b)

C₃H₉

c)

C₂H₆

d)

CH₃

13.

What is the correct setup to determine how many grams a 15.0 L sample of O2 at STP will be? (Hints: molar mass of O = 16.00 g, 1 mole = 22.4 L)

a)

$15.0\ L\ x\ \frac{1\ mole}{22.4\ L}\ x\ \frac{32.00\ g}{1\ mole}\ =\$

b)

$15.0\ L\ x\ \frac{1\ mole}{22.4\ L}\ x\ \frac{16.00\ g}{1\ mole}\ =$

c)

$32.00\ g\ x\ \frac{1\ mole}{15.0\ L}\ x\ \frac{22.4\ g}{1\ mole}\ =$

d)

$15.0\ L\ x\ \frac{1\ mol}{32.00\ g}x\ \frac{22.4\ L}{1\ mol}=$

14.

How many grams would a 2.50 x 10²³ atom sample of copper be? The molar mass of copper is 63.55 g/mol. Round answer to correct amount of sig figs.

(a)

Unit 4.2-4.3 Review (Molar Mass and Chemical Composition)

Total questions: 14

Worksheet time: 10mins

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