Mole Unit Problems
1.
How many molecules of methane are there in 2.50 moles of methane (CH4)?
2.50 moles x 6.02 x 1023 molecules
1 mole
2.
How many moles of Zn is 4.22 x 1027 atoms of Zinc?
4.22 x 1027 atoms Zn x
3.
1 mole Fe
55.845g Fe
= 242 g SO2
= 0.451 moles Fe
What is the volume in liters of 3.76 moles of chlorine (Cl2) at STP?
3.76 moles Cl2 x
6.
64.06 g SO2
1 mole SO2
How many moles is 25.2g of iron?
25.2g Fe x
5.
1 mole Zn
= 7010 moles Zn
6.02 x 1023 atoms Zn
Calculate the mass of 3.78 moles of sulfur dioxide.
3.78 moles SO2 x
4.
= 1.51 x 1024 molecules
22.4 L Cl2
1 mole Cl2
= 84.2 L of Cl2
How many moles is 18.5 liters of carbon dioxide gas at STP?
18.5 L CO2 x
1 mole CO2
22.4 L CO2
= 0.826 moles CO2
7.
How many atoms are in 16.5 g of silver?
16.5g Ag x
8.
1 mole
x
107.8682g Ag
M =
1 mole NaOH
39.997g NaOH
1.05 moles NaOH
0.55 L solution
= 1.05 moles NaOH
= 1.9 M
How many grams of hydrochloric acid are in 45mL of a 0.50M solution?
0.50M =
x moles HCl
0.045L solution
0.023 moles HCl x
10.
= 9.21 x 1022 atoms Ag
What is the molarity of a solution in which 42.0g of sodium hydroxide is
dissolved in 550mL of solution.
42.0g NaOH x
9.
6.02 x 1023 atoms
1 mole Ag
= 0.023 moles HCl
36.46g HCl
1 moles soln
= 0.84g HCl
What volume of 2.3 M potassium sulfate solution could be made with 63.0g of the
compound?
63.0g K2SO4 x
1 mole K2So4 = 0.36 moles K2SO4
174.26g K2SO4
2.3M = 0.36 moles K2SO4
x liters solution
x = 0.16 L solution
12.
What is the % composition of a compound in which 13.4 grams of nickel
combines completely with 3.7 g of oxygen?
13.4g Ni x 100 = 78%
3.7g O x 100 = 22%
17.1g
17.1g
13..
Find the percent composition of a compound containing tin and chlorine if 18.35g
of the compound contains 5.74g of tin.
5.74g Sn x 100 = 31.3%
12.61g Cl x 100 = 68.7%
18.35g
18.35
14.
Calculate the percent of each element present in potassium phosphate from its
formula.
K3PO4 molar mass = 212.266g
117.2949g K x 100 = 55% K
212.266g
30.97376g P x100 =15% P
212.266g
63.9976g O x 100 = 30% O
212.266g
15.
Calculate the percent composition of propane C3H8.
C3H8 molar mass = 44g
36g C x 100 = 82% C
44g
16.
How many grams of hydrogen are in 350 grams of propane (C3H8)?
3.50g C3H9 x
17.
18g H
= 63g H
100g C3H8
A compound is found to contain 40% silver. How many grams of silver would
there be in 120 grams of this compound?
120g Ag x
18.
8g H x 100 = 18% H
44g
40g Ag
= 48g Ag
100g compound
How many grams of iron can be recovered from 639g of iron(III) oxide?
Fe2O3 molar mass = 159.6882g
111.69g Fe x 100 = 69.9%
159 6882g
639g Fe2O3 x
47.9982g O x 100 = 30.1%O
159.6882g
69.9g Fe = 447g Fe
100g Fe2O3
19.
Determine the empirical formula of the compound with the percent composition
of: 29.1% Na, 40.5% S, and 30.4% O.
29.1g Na x
40.5g S x
1 mole Na = 1,27 moles Na / 1.26 = 1 x 2 = 2
22.9898g Na
1 mole S
32.065g S
= 1.26 moles S / 1.26 = 1 x 2 = 2
Na2S2O3
sodium thiosulfate
30.4g O x
20.
1 mole O = 1.90 moles O / 1.26 = 1.5 x 2 = 3
15.9994g O
A compound is 85.7% carbon and 14.3% hydrogen. What is the empirical
formula?
85.7g C x
1 mole C = 7.14 moles / 7.14 = 1
12.011g C
14.3g H x 1 mole H = 14.2 moles / 7.14 = 2
1.00794g H
C1H2
If the molar mass of the compound above is 42.0g, what is the molecular formula?
CH2 molar mass would be 14g
21.
42.0g = 3
14g
C3H6
You find that 7.36 g of a compound has decomposed to give 6.93 g of oxygen.
The rest of the compound is hydrogen. What is the empirical formula?
6.93g O x
1 mole O = 0.433 moles / 0.427 = 1
15.9994g O
0.43g H x 1 mole H = 0.427 moles / 0.427 = 1
1.00794g H
O1H1
If the molar mass of the compound above is 34.0 grams, what is the molecular
formula?
O1H1 molar mass would be 17g
34,0g = 2
17g
H2O2