SAMPLE PROBLEM 18.7
Determining concentrations from Ka and initial [HA]
PROBLEM:
Propanoic acid (CH3CH2COOH, simplified as HPr) is an organic acid whose salts are used to retard mold growth in foods. What is the [H3O+] of a 0.10 M aqueous solution of HPr (Ka = 1.3 x 10-5)?
SOLUTION:
x = [HPr]diss = [H3O+]from HPr = [Pr-]
concentration (M)
Since Ka is small, we assume that x << 0.10
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