Unit 6 - Solutions
Section 2 – Solution Concentration
1. If 6.73 g of Na2CO3 is dissolved in enough water to make 250. mL of solution, what is the molarity of the sodium
carbonate? What are the molar concentrations of the Na+ and CO32− ions?
2. What is the mass, in grams, of solute in 250. mL of a 0.0125 M solution of KMnO 4?
3. What volume of 0.123 m NaOH, in milliliters, contains 25.0 g of NaOH?
4. If 4.00 mL of 0.0250 M CuSO4 is diluted to 10.0 mL with pure water, what is the molarity of copper(II) sulfate in
the diluted solution?
5. If you need 1.00 L of 0.125 M H2SO4, which of the following methods would you use to prepare this solution?
a. Dilute 20.8 mL of 6.00 M H2SO4 to a volume of 1.00 L.
b. Add 950. mL of water to 50.0 mL of 3.00 M H2SO4.
6. For each solution, identify the ions that exist in aqueous solution & specify the concentration of each.
a. 0.25 M (NH4)2SO4
b. 0.056 M HNO3
c. 0.123 M Na2CO3
d. 0.00124 M KClO4
7. If I make a solution by adding 83 grams of sodium hydroxide to 750 mL of water:
a. What is the molality of sodium hydroxide in this solution?
b. What is the percent by mass of sodium hydroxide in this solution?
c.
What is the mole fraction of sodium hydroxide in this solution?
8. If I make a solution by adding water to 35 mL of methanol (CH3OH) until the final volume of the solution is 275
mL:
a. What is the molarity of methanol in this solution? (The density of methanol is 0.792 g/mL)
b. What is the percent by volume of methanol in this solution?
9. In medicine it is sometimes necessary to prepare solutions with a specific concentration of a given ion. A lab
technician has made up a 100.0 mL solution containing 0.50 g of NaCl and 0.30 g of KCl, as well as glucose and
other sugars. What is the molarity of the chloride ions in the solution?
10. The concentration of toxic chemicals in the environment is often measured in parts per million (ppm) or even
parts per billion (ppb). A solution in which the concentration of the solute is 3 ppb by mass has 3 g of the
solution for every billion grams of the solution. The World Health Organization has set the acceptable standard
for lead in the drinking water at 10 ppb. In 1992 the tap water in one-third of homes in Chicago was found to
have a lead concentration of 10 ppb. If you lived in one of these homes and drank 2 L of tap water at home each
day, what is the total mass of lead you would have ingested per year?