How much 10.0 M HNO3 must be added to 1.00 L of a buffer that is 0.0100 M acetic acid and 0.100 M sodium acetate to reduce the pH to 5.00? pKa of acetic acid= 4.75

Answer 1

1000 mL x 0.01M = 10 millimols HAc
1000 mL x 0.1M = 100 mmols NaAc

..........Ac^- + H^+ ==> HAc
I........100.....0........10
add HNO3.........x...........
C........-x.....-x.........+x
C.......100-x....0........10+x

pH = pKa + log [(100-x)/(10+x)]
Solve for x = mmols HNO3 needed.
M = mmols/mL. You know mmols and M, solve for mL HNO3. I think the answer is about 3 mL.