Chemistry 121A Hanson
Molarity Practice Problems
1. How many moles of K+ are in 10.0 mL of 0.1250 M K2CO3 solution?
2. How many g of NaOH (MW 40.00) are needed to make 250 mL of 0.1250 M NaOH solution?
3. How many mL of 0.1250 M NaOH solution are required to make 15.0 mL of 0.0100 M NaOH
solution?
4. What is the concentration of ammonium ion in a solution that is made by adding 30.0 mL of
water to 50.0 mL of a 0.1250 M (NH4)3PO4 solution?
5. How many grams of (NH4)3PO4 (MW 149.1) is in the solution made in (4)?
6. How many mL of 0.15 M K2CO3 are required to make 100 mL of 0.03 M K+ solution by
dilution?
7. What volume of 0.150 M NaOH solution is required to react completely with 50.0 mL of 0.200
M HCl solution?
8. What volume of 0.120 M NaOH solution is required to react completely with 40.0 mL of 0.200
M H2SO4 solution?
9. A 0.5010 g sample of diprotic acid H2A (MW 120.0) is titrated with 35.0 mL of an NaOH
solution. What is the concentration of the NaOH solution?
10. If, in a titration, 0.2520 g of an unknown diprotic acid "H2X" requires 15.00 mL of 0.2390 M
NaOH to reach the equivalence point, what is the molar mass of H2X?
11. 25.00 mL sample of a 0.200 M K2C2O4 solution is reacted with 5.76 mL of a 0.400 M KMnO4
solution according to the following chemical equation:
5 C2O42– + 2 MnO4– + 16 H+  10 CO2 (g) + 2 Mn2+ + 8 H2O
(a) What is the limiting reactant?
(b) How many moles of carbon dioxide are produced in this reaction?
(c) What volume of carbon dioxide gas is produced if it is collected at 744 mmHg and 25 oC?
12. How many cubic meters of air at 25.0 °C and 1.00 atm is needed to completely burn 355 g of
propane (C3H8, MW 44.1). Assume that the air is composed of 21.0 mol% O2.
Answers
1. 0.00250
2. 1.25
3. 1.20
4. 0.234 M
5. 0.932
6. 10
7. 66.7 mL
8. 133 mL
9. 0.239 M
10. 141 g/mol
11. (a) K2C2O4 (b) 0.010 (c) 0.25
12. 4.69