Question

A 240.0 mL buffer solution is 0.290 M in acetic acid and 0.290 M in sodium acetate.

Part A: What is the initial PH of this solution?

Part B: What is the PH after addition of 0.0150 mol of HCL?

Answer 1

For acetic acid

A 240.0 mL buffer solution is 0.290 M in acetic acid and 0.290 M in sodium acetate.
Part A: The initial PH of this solution is equal to pKa of acetic acid which is 4.74.

Note: When [acetic acid] = [sodium acetate] , pH =pKa

Part B: After addition of 0.0150 mol of HCl.

Number of moles of acetic acid before addition of 0.0150 mol of HCl

Number of moles of sodium acetate before addition of 0.0150 mol of HCl

Note: 240.0 mL are converted into 0.240 L by using expression 1 L = 1,000 mL.

After addition of 0.0150 mol of HCl.

Number of moles of sodium acetate after addition of 0.0150 mol of HCl

Number of moles of acetic acid after addition of 0.0150 mol of HCl