Question

Match the formulas of the following acids with their correct names.
Acids –
(a) $HCl$
(b) $HN{O_3}$
(c) ${H_2}S{O_4}$
(d) ${H_2}C{O_3}$
Names-
1.Carbonic acid
2.Sulphuric acid
3.Hydrochloric acid
4.Nitric acid

Answer 1

We need to know the elements which make up the acid in order to name it. Acids mandatorily have hydrogen as the cation. The first step is to identify the elements present in the acid other than the hydrogen by observing the molecular formula. The acids are named based to the anions attached to the hydrogen and accordingly the prefix and the suffix are decided. Also, some acids have oxygen in them and another set of rules comply in naming them.

Complete step by step answer:
Now we discuss the simple set of rules for naming acids as,
As we know that acids contain a mandatory hydrogen ion, simple acids which have only one anion attached to the hydrogen are known as binary acids. Such acids are named with the prefix “hydro-“followed by the first syllable of the anion and adding the suffix “-ic”.
With acids having oxygen in them, a polyatomic ion is formed instead of simply an anion (hence not binary). The polyatomic ion itself ends with the suffix “-ate” which is replaced by the suffix “-ic” for giving the acid name.
When polyatomic ions have one extra oxygen (different from a typical polyatomic atom),the acid names have the prefix “per-“ and the suffix “-ic”. In contrast, polyatomic ions which have one less oxygen, the acid names have the suffix “-ous” and those with two oxygen less have the prefix “hypo-“ and the suffix “ous-“.
If a polyatomic ion has the suffix “-ate” ,it gets replaced by the suffix “-ic” in its acid name.
Following these rules, let us name the given acids by their molecular formulas:
(a) $HCl$ : This is an example of a binary acid and according to rule (i), it is named as Hydrochloric acid,
(b) $HN{O_3}$ : This has a polyatomic ion called nitrate ion and according to rule (iv), it is named as Nitric acid.
(c) ${H_2}S{O_4}$ :This has a polyatomic ion called sulphate ion and according to rule (iv), it is named as Sulphuric acid.
(d) ${H_2}C{O_3}$ : This has a polyatomic ion called carbonate ion and according to rule (iv), it is named as carbonic acid.
Therefore,
(a) $HCl$ - (3) Hydrochloric acid
(b) $HN{O_3}$ - (4) Nitric acid
(c) ${H_2}S{O_4}$- (2) Sulphuric acid
(d) ${H_2}C{O_3}$ - (1) Carbonic acid

Note:
We have to note there are additional sets of rules for naming rules with more complex ions. For example polyatomic ions which have an additional oxygen than the “-ate” ion, then the acid is named with the prefix “per-” followed by the suffix “-ic.” For example, the polyatomic chlorate ion is $Cl{O_3}^-$ and therefore according to this rule its acid $HCl{O_4}$ is named as perchloric acid.Also if the polyatomic ion as one less oxygen than the “-ate” ion, the acid has the suffix “-ous.” For example, chlorous acid is $HCl{O_2}$
If the polyatomic ion has two less oxygen than the “-ate” ion, the prefix is “hypo-” and the suffix will be “-ous.” For example hypobromous acid, $HBrO$ .