Question

1) How would you make 300 ml of a 0.1 M sodium phosphate buffer, pH 7.0 (pKa = 7.2) phosphate dibasic (the conjugate base).

2) What are the concentrations of acetate and acetic acid in a 0.2 M acetate buffer pH 5.3? The pKa for acetic acid is 4.76.

3)You have 100 ml of 0.1 M acetate buffer pH 5.2 (pKa 4.76). You add 10 ml of 0.1 M NaOH. Calculate the resulting change in pH and the buffering capacity (pH/mmol) of the solution. Perform the same buffering capacity calculation for addition of 10 ml of 0.1 M HCl. (Assume strong acids and bases ionize 100%).

4)Calculate the molar extinction coefficient of PNPG at 420 nm from the following data. You prepare two ONPG standards, one at 10 M and one at 2 M. The absorbances at 420 nm were 0.366 and 0.069 respectively.

Answer 1