Molar Mass, Hydrates, Empirical and Molecular Formulas Test
Test #: _____
Super Easy
1. Calculate the molar mass and percent composition of KClO3. (3.5 out of 5)
2. What is the mass of 0.500 moles of KClO3? (3.5 out of 5)
3. How many moles are there in 30.0 g of KClO3? (3.5 out of 5)
Easy
1. Calculate the molar mass and percent composition of barium nitrate. (4 out of 5)
2. What is the mass of 1.50 moles of barium nitrate? (4 out of 5)
3. How many moles are there in 40.0 g of barium nitrate? (4 out of 5)
Average
1. Calculate the molar mass and percent composition of magnesium phosphate. (5 out of 5)
2. What is the mass of 2.50 moles of magnesium phosphate? (5 out of 5)
3. How many moles are there in 50.0 g of magnesium phosphate? (5 out of 5)
Difficult
1. Calculate the molar mass and percent composition of nickelic carbonate. (6 out of 5)
2. What is the mass of 2.50 moles of nickelic carbonate? (6 out of 5)
3. How many moles are there in 50.0 g of nickelic carbonate? (6 out of 5)
Super Easy
4. Calculate the molar mass and percent of water of Na2CO3  H2O. (3.5 out of 5)
5. What is the mass of 3.50 moles of Na2CO3  H2O? (3.5 out of 5)
6. How many moles are there in 60.0 g of Na2CO3  H2O? (3.5 out of 5)
Easy
4. Calculate the molar mass and percent water of calcium bromide pentahydrate. (4 out of 5)
5. What is the mass of 3.50 moles of calcium bromide pentahydrate? (4 out of 5)
6. How many moles are there in 60.0 g of calcium bromide pentahydrate? (4 out of 5)
Average
4. Calculate the molar mass and percent water of barium phosphate trihydrate. (5 out of 5)
5. What is the mass of 3.50 moles of barium phosphate trihydrate? (5 out of 5)
6. How many moles are there in 60.0 g of barium phosphate trihydrate? (5 out of 5)
Difficult
4. Calculate the molar mass and percent water of stannous phosphate tetrahydrate. (6 out
of 5)
5. What is the mass of 3.50 moles of stannous phosphate tetrahydrate? (6 out of 5)
6. How many moles are there in 60.0 g of stannous phosphate tetrahydrate? (6 out of 5)
7. If you heated 5.00 g of the hydrate, how much water would evaporate? (same amount
of points as in numbers 4 – 6).
8. If you heated 5.00 g of the hydrate, how much anhydrous salt would remain? (same
amount of points as in numbers 4 – 6).
A student gathers the following data doing the hydrate lab:
Mass of crucible
Mass of crucible & CuSO4  5 H2O
Mass of crucible & CuSO4
20.63 g
30.69 g
27.28 g
9. Using this data, calculate the percent water of the hydrate. (5 points)
10. What is the percent error? (5 points)
Empirical Formula Math Problems
11. Find the empirical formula for a compound that is 20.2 % magnesium, 26.6 % sulfur,
and 53.2 % oxygen. (5 points)
12. Find the empirical formula for a compound that contains 0.432 g of magnesium,
0.214 g of carbon, and 0.854 g of oxygen. (5 points)
Easy - If you get this correct, you can earn a maximum of 3.5 out of 5 points.
13. Determine the molecular formula of a compound having an empirical formula of NS2
and a molar mass of 156.4 g/mol.
Average – If you get this correct, you can earn a maximum of 5 out of 5 points.
13. A substance is composed of 80.0 % C and 20.0 % H. It has a molar mass of 30.0 g.
What is the molecular formula?
Difficult – If you get this correct, you can earn a maximum of 6 out of 5 points.
13. A substance is known to be composed of oxygen, chlorine, and potassium. 31.84 g of
the substance is decomposed into a solid and a gas. It is determined that the solid has
a mass of 19.36 g and is 52.4 % potassium and 47.6 % chlorine. The original
compound has a molar mass of 122.6 g. What is the molecular formula?
Name: ______________________________________________
Molar Mass, Hydrates, Empirical and Molecular Formulas Test
Test # _____
K 31.9
Cl 28.9
O 39.2
122.6
Ba 52.5
N 10.7
O 36.7
261.3
Mg 27.7
P 23.6
O 48.7
262.9
Ni+3 39.5
C 12.1
O 48.4
297.4
61.3
392
657
744
0.245
0.153
0.190
0.168
Na
C
O
1 H2O 14.5
124
434
Ca
Br
5 H2O 31.0
290
Ba
P
O
3 H2O 8.23
656
2.30 x 103
2300
Sn+2
P
O
4 H2O 11.6
618.1
2160
0.484
0.207
0.0915
0.0971
0.725
1.55
0.412
0.580
4.28
3.45
4.59
4.42
1020
9
3.41/10.06 = 33.9
10
36.1-33.9/36.1 = 6.1
11
20.2/24.3 = 0.831
26.6/32.1 = 0.829
53.2/16 = 3.325
MgSO4
12
0.432/24.3 = 0.0178
0.214/12 = 0.0178
0.854/16 = 0.0534
MgCO3
13
NS2 = 78.2
156/78.2 = 2
N2S4
80/12 = 6.66
20/1 = 20
CH3 = 15
30/15 = 2
C2H6
19.36 = 0.524
= 0.476
10.14/39.1 = 0.259
9.22/35.5 = 0.260
12.46/16 = 0.779
KClO3