The table gives the names and structural formulae of the first four members of the homologous series of carboxylic acids. One structural formula is missing.
Table: The names and structural formulae of the first four carboxylic acids
| Name of carboxylic acid | Structural formula |
|---|---|
| Methanoic acid | HCOOH\text{HCOOH}HCOOH |
| Ethanoic acid | CH3COOH\text{CH}_3\text{COOH}CH3COOH |
| Propanoic acid | |
| Butanoic acid | CH3CH2CH2COOH\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}CH3CH2CH2COOH |
Complete the table by giving the structural formula of propanoic acid.
Use the table to explain how the structural formulae show that all four of these compounds are carboxylic acids.
Ethanoic acid dissolves in water. Give the pH of the solution formed, and explain your answer.