What are the concentrations of benzoic acid and sodium benzoate in a solution that is buffered with a pH of 4.55 and has a freezing point of -2.0 degrees Celsius? (assume complete dissociation and a density of 1.01g/mL for the solution.)

Answer 1

Several steps to this problem. Here is an outline.
1. Use the HH equation and solve for the ratio of base/acid; i.e., sodium benzoate to benzoic acid. Then convert that to percent of each.

2. Use the percents to calculate a van't Hoff factor. That is 2*%base + 1*%acid = total = i

3. Use delta T = iKf*m and solve for m

4. Use density to convert molality to molarity

5. Use the percents to convert to M of each component.
Good luck. Post your work if you get stuck.