Question

(a) Write the structural formula for pentan-1-oic aicd.
(b) What happens when acetic acid reacts with sodium carbonate?

[3 Marks]

Answer 1

(a) Given the IUPAC name is pentan-1-oic acid.

Since the root word is pent, there will be five carbons in the parent chain.[0.5 Marks]

The primary suffix is -an-, all the carbon atoms linked with only single bonds in the main carbon chain and the secondary suffix is -oic acid, so the funtional group is carboxylic acid (-COOH). [0.5 Marks]

The position of the funtional group is on the first carbon (-1-oic acid).
Therefore the structural formula is ${\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{CH}}_2\text{COOH}$. [1 Mark]

(b) Sodium carbonate reacts with acetic acid to form sodium acetate, carbon dioxide gas and water. The reaction takes place as follows:

${\text{2CH}}_3\text{COOH (l)}+{\text{Na}}_2{\text{CO}}_3\text{(s)}⟶2{\text{CH}}_3\text{COONa(aq)}+{\text{H}}_2\text{O(l)}+{\text{CO}}_2\text{(g)}$
[1 Mark]