This question is about two different types of organic acids: carboxylic acids and sulfonic acids.
Predict the bond angles aaa and bbb and name the molecular shapes around the central atom for:
- The carbonyl carbon in a carboxylic acid, bond angle aaa.
- The oxygen atom of the hydroxyl group in a sulfonic acid, bond angle bbb.
Benzoic acid, C6H5COOH\text{C}_6\text{H}_5\text{COOH}C6H5COOH, and benzenesulfonic acid, C6H5SO2OH\text{C}_6\text{H}_5\text{SO}_2\text{OH}C6H5SO2OH, are both monobasic acids. Their pKa\text{p}K_apKa values are shown in the table below:
| Acid | Formula | pKa\text{p}K_apKa |
|---|---|---|
| Benzoic acid | C6H5COOH\text{C}_6\text{H}_5\text{COOH}C6H5COOH | 4.20 |
| Benzenesulfonic acid | C6H5SO2OH\text{C}_6\text{H}_5\text{SO}_2\text{OH}C6H5SO2OH | -2.80 |
A student claims that a 0.10 mol dm−30.10\text{ mol dm}^{-3}0.10 mol dm−3 solution of benzenesulfonic acid will have a lower pH\text{pH}pH value than a 0.10 mol dm−30.10\text{ mol dm}^{-3}0.10 mol dm−3 solution of benzoic acid.
Write an equation, showing conjugate acid–base pairs, for the equilibrium of C6H5SO2OH\text{C}_6\text{H}_5\text{SO}_2\text{OH}C6H5SO2OH with water, and explain with reasons whether the student's claim is correct. Label the conjugate acid–base pairs as A1, B1 and A2, B2.