[StudyGuide]

I am reviewing questions and here are some of the ones I can't seem to figure out.

1.Calculate the pH of a solution formed by mixing 25mL of 0.1M acetic acid with 12.5 mL of 0.2M NaoH- The right answer is supposed to be 8.79.

Here's where I am stuck-
Acid added is 0.025L x 0.1M acetic acid =0.0025
Base added is 0.0125L x .2M NaOH=0.0025

After addition acid=0.0025-0.0025=0 mol of acid after addition
0 mol of acid/(0.0025=0.0025)=0
But log of 0 gives me error
where do I go from here? Did I do that right?

2. What is the resultant pH when 10.0mL of 0.950M NaOH is added to 100ml of a buffer solution that consists of 0.10M CH3COOH and 0.10M NaCH3COO. Ka for CH3COOH is 1.85x10^-5. The right answe is supposed to be 6.3

when I try the henderson-hasslebach Equation (pH=pKa+log(Ha?A-) for this question I get the wrong answer.

Thanks a lot for your help.

[Donaldson Tan]

1. although there is complete neutralisation between acetic acid and NaOH, recall that acetate is a strong base and it undergoes hydrolysis readily, thus the pH of the solution is more than 7.

2. did u take in account of volume changes?

[AWK]

1. Calculate concentration of salt in the final volume and pH for salt hydrolysis

2. NaOH reacts with CH3COOH and you will get a new buffer solution with decreased amount (concentration) of CH3COOH and increased amount (concentration) of salt.