Question

Find the molecular mass of $sulphuric$acid.

Answer 1

Sulphuric Acid is a well-known acid which is used to prepare phosphoric acid in chemical industries, in the fertilizer manufacture, to make synthetic dyes and explosives. The oxidation state of sulphur here is $+ 6$.

Complete step by step answer:
SulphuricAcid is a very important acid in the chemical industry. It is manufactured by a very famous method “Contact process”. In this method $S{O_2}$ is oxidised to $S{O_3}$ by catalytic surface.

2S{O_2}(g) + {O_2}(g) \to 2S{O_3}(g) \\\ S{O_3} + {H_2}S{O_4} \to {H_2}{S_2}{O_7} \\\ {H_2}{S_2}{O_7} + {H_2}O \to 2{H_2}S{O_4} \\\ \end{gathered} $$ Formerly a platinum gauze or platinized asbestos was used as catalyst. But nowadays ${V_2}{O_5}$ is used as a catalyst which is a transition metal oxide. This catalyst is slightly less cheap but economical and easily poisoned. $${H_2}{S_3}{O_{10}} + 2{H_2}O \to 3{H_2}S{O_4}$$ Sulphuric acid has a melting point of${10.5^\circ }C$. It forms a viscous liquid after melting. It is strongly hydrogen bonded but it does not react with metals to produce hydrogen gas $({H_2})$ in absence of water $({H_2}O)$. $Fe + {H_2}S{O_4} \to FeS{O_4} + {H_2} \uparrow $ Also the acid is a very strong oxidising agent as it reacts with sodium bromide to form hydrogen bromide and bromine gas. $\begin{gathered} NaBr + {H_2}S{O_4} \to NaHS{O_4} + HBr \\\ 2HBr + {H_2}S{O_4} \to B{r_2} \uparrow + S{O_2} \uparrow + 2{H_2}O \\\ \end{gathered} $ It also oxidises some non-metals $$\begin{gathered} 3S + {H_2}S{O_4} \to 3S{O_2} \uparrow + 2{H_2}O \\\ C + {H_2}S{O_4} \to C{O_2} \uparrow + S{O_2} \uparrow + 2{H_2}O \\\ \end{gathered} $$ In dilute solutions it acts as a very strong acid. The first proton of the acid dissociates very rapidly to form $HSO_4^ - $ and the second proton dissociates very slowly. Thus the dissociation constant of Sulphuric Acid can be represented as ${K_{a1}} \ll {K_{a2}}$ The chemical formula of Sulphuric Acid is$${H_2}S{O_4}$$. Thus its molecular mass of$S = 32gm$;$H = 1gm$ $O = 16gm$ $\begin{gathered} \therefore Massof{H_2}S{O_4} = 2 \times 1 + 32 + 4 \times 16 \\\ \Rightarrow Massof{H_2}S{O_4} = 2 + 32 + 64 \\\ \Rightarrow Massof{H_2}S{O_4} = 98gm \\\ \end{gathered} $ Hence the molecular mass of SulphuricAcid is equal to$98gm$.The sulphate ion ( $SO_4^{2 - }$) is tetrahedral. All the bond lengths are the same and shorter. The bond order of $S - O$ bond is$1.5$. **Note:** Like Sulphuric Acid, Hydrochloric acid and Nitric acids are very strong and also strong oxidising agents. For this reason $HCl$ and $HN{O_3}$ cannot be used in the acidic medium of Potassium permanganate $(KMn{O_4})$.