Question

Part #1: You obtain a buffer that 0.414 moles of chlorous acid (HClO2, Ka = 1.10 x 10-2) and 0.414 moles of potassium chlorite (KClO2) dissolved in 1.00 L of solution. What is the pH of the buffer?

Part #2: To the buffer in part 1, you add 0.200 moles of potassium hydroxide (KOH). Write the reaction of the buffer with the base. After, complete an ICE table calculating the END moles of each substance after the reaction. Hint: consider potassium hydroxide to react COMPLETELY. Which of the following represents the END moles of HClO2 and ClO2- after reaction?

A HClO2: 0.614 moles ClO2-: 0.214 moles B HClO2: 0.214 moles ClO2-: 0.214 moles C HClO2: 0.214 moles ClO2-: 0.614 moles D HClO2: 0.614 moles ClO2-: 0.614 moles

Part#3: What is the pH of the solution in part 2 after the reaction with KOH?

Part #4: In a separate container, there are 0.282 moles of HClO2 and 0.414 moles of ClO2- dissolved in 1.00 L of solution. What is the pH of this solution?

Part #5: To the solution in part 4, you add the same number of moles of KOH as was added in part 2 (0.200 moles). What is the final pH of this solution after the reaction occurs?

Part #6: You remake the solution in part 1 (0.414 moles HClO2 and 0.414 moles ClO2- dissolved in 1.00 L). What is the minimum number of moles of KOH would need to be added in order to 'overwhelm' this buffer?

Part #7: You remake the solution in part 4 (0.282 moles HClO2 and 0.414 moles ClO2- dissolved in 1.00 L). What is the minimum number of moles of KOH would need to be added in order to 'overwhelm' this buffer?

Part #8: Which solution represents the 'best' buffer, and why?

A The solution in part 4 because the pH won't change much if a solution of strong acid is added

B The solution in part 1 because the pH is closer to the pH of a solution of the weak acid

C The solution in part 1 because the buffer requires more strong base or strong acid to overwhelm the buffer

D The solution in part 4 because the pH is closer to the pH of water

Answer 1