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Solubility and pH of ethanoic acid
Not surprisingly, carboxylic acids are acidic! They are weak acids as they are only partially ionised in solution. For example, 0.1M ethanoic acid is about pH 3 which means only about 1 in 100 acid molecules is ionised. Their acidity is due to the delocalisation of the acid anion charge over the two oxygen atoms:
You should see that these two ions are identical, and so the real structure is exactly in between these two extremes. This means that there is only half a negative charge on each oxygen atom. This makes it relatively easy for the H+ ion to escape from the oxygen atom to which it was attached.
Sodium carbonate solution reacts readily with ethanoic acid releasing carbon dioxide gas:
|
Na2CO3(aq) + 2CH3COOH(aq) ⇒ 2CH3COONa(aq) + H2O(l) + CO2(g) |
The smaller carboxylic acids are readily soluble in water because the carboxylic acid group is hydrophilic as it can hydrogen bond to water. However, as the hydrophobic carbon chain becomes longer the solubility of the acid drops rapidly.
