# Finding pH of solution

1. Nov 18, 2012

### Rron

A solution is prepared by mixing 200 mL of 0.2 M CH3COOH with 100 mL of 0.1 M of NaOH solution.Calculate the pH of the solution.(Ka=1.8x10-5)

I really don't know how to start this, so please help me.Its gonna be a similar one on my exam tomorrow.

Thanks.

2. Nov 19, 2012

### chemisttree

Assume the strong base completely converts the acetic acid to acetate. From there look at the expression which defines Ka for this acid. That's a start.

If you can't see it from that information, try looking over this information.

3. Nov 20, 2012

### Staff: Mentor

Hint: have you heard about buffers?

4. Nov 24, 2012

### salger12

This is a buffer question. You will need to set up two ICE tables. The first one outlines the remaining concentration of weak acid and conjugate base after the reaction with OH-. The second should use those concentrations to determine the final pH. If you have a book, there should be an example.

5. Nov 24, 2012

### Staff: Mentor

Actually no need even for a single ICE table, this is almost a simple plug and chug application of the Henderson-Hasselbalch equation. You just need to start calculating concentrations of the reaction products, assuming reaction went to completion.

6. Nov 24, 2012

### salger12

Correct, the Henderson-Hasselbalch equation is the preferred method. If this student does not know where to start, however, I figured writing out the concentration ratios would help in gaining some intuition.