# Calculating equilibrium constant

1. May 13, 2008

### kasse

1. The problem statement, all variables and given/known data

Find the eq. constant for the reaction

CH3COOH (aq) + NO2- (aq) = CH3COO- (aq) + HNO2 (aq)

3. The attempt at a solution

I find Ka for the reaction CH3COOH = CH3COO- + H+ and Kb for the reaction NO2- + H+ = HNO2

But what are the rules then? I try multiplying the constants, but this does not give the correct answer.

2. May 13, 2008

### eli64

write the K expression for this equilibrium

then compare it to the Ka expressions for both CH3CO2H AND HNO2

3. May 13, 2008

### kasse

I managed to find the correct solution by multiplying Ka1 and the 1/Ka2. Is 1/Ka2 the same av Kb?

4. May 14, 2008

### Staff: Mentor

5. May 14, 2008

### eli64

Did you just happen to work out the numbers and find the right answer or did you see that rearranging the Ka expressions for the acids gave Ka(CH3CO2)/Ka(HNO2) which was equal to the K expression for the original equilibrium?