Question

You are asked to go into the lab and prepare an acetic acid - sodium acetate buffer solution with a ph of 4.00  0.02. what molar ratio of ch3cooh to ch3coona should be used?

Answer 1

Hello!

To solve this problem we are going to use the Henderson-Hasselbach equation and clear for the molar ratio. Keep in mind that we need the value for Acetic Acid's pKa, which can be found in tables and is 4,76:

 $pH=pKa + log ( \frac{[CH_3COONa]}{[CH_3COOH]} )$

$\frac{[CH_3COOH]}{[CH_3COONa}= 10^{(pH-pKa)^{-1}}=10^{(4-4,76)^{-1}}=5,75$

So, the mole ratio of CH₃COOH to CH₃COONa is 5,75

Have a nice day!