45 mL x 0.15M NaF = 6.75 mmoles NaF.
35 mL x 0.10M HF = 3.5 mmoles HF.
5 mL x 0.05M HCl = 0.50 mmoles H^+.
...............F^- + H^+ ==> HF
initial......6.75....0......3.50
add HCl.............0.25........
change.......-0.25..-0.25....+0.25
equil........6.50....0.......3.75
Substitute these numbers into the HH equation and solve for pH. Check my work.
A buffer is prepared by mixing 45.0 mL of 0.15 M NaF to 35.0 mL of 0.10 M HF (Ka = 6.8x10^-4) Calculate the pH of this buffer after 5.0 mL of 0.05 M HCl is added.
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