# Chapter 12 Lecture Problems

## Concentration

1. Calculate the concentration (molarity) of a solution prepared by dissolving 12.00 grams of potassium chloride in water and diluting to 250.0 mL.

2. Calculate the concentration (molality) of a solution prepared by dissolving 12.00 g of KCl in 250.0 mL of water at 20 °C.

3. Calculate the concentration (mole fraction) of KCl in a solution prepared by dissolving 12.00 g of KCl in 250.0 mL of water at 20 °C.

4. Calculate the concentration (weight percent) of KCl in a solution prepared by dissolving 12.00 g of KCl in 250.0 mL of water at 20 °C.

5. Calculate the ppm by mass of KCl in a solution prepared by dissolving 0.01200 g of KCl in 250.0 mL of water at 20 °C.

6. Solutions

## Colligative Properties

1. Lecture Problem: How much CO2 (grams) will dissolve in 2 L of water when PCO2 = 4 atm and the temperature is 25 oC. kH = 4.48 x 10-5 M mmHg-1.

2. Lecture Problem: Mix 100 g of water (vapor pressure 23.756 torr) with 500 g methanol, CH3OH (vapor pressure 15.68 torr). Calculate Pwater, PMethanol, Ptotal.

3. Lecture Problem: Add 20.00 g fructose (C6H12O6) to 500 mL H2O. What is the freezing point? What is the boiling point?

4. Lecture Problem: Add 20.00 g NaCl to 500 mL H2O. What is the freezing point? What is the boiling point?

5. Lecture Problem: What pressure is required to purify seawater using reverse osmosis? Assume that the initial concentration of NaCl is approximately 0.5 mole liter-1 and that it must be purified to 1x10-4 mole liter-1.

6. Solutions: