Question

Match the following tests for sulphuric acid with the result to confirm its presence.

• A. Colour change
• B. White fumes
• C. White precipitate

Answer 1

1. Potassium dichromate $\left(K_{2}C{r}_2{O}_7\right)$ test : The orange coloured (${\text{K}}_2{\text{Cr}}_2{\text{O}}_7)$ turns green in the presence of sulphuric acid.

2. Ammonia test: Dense white fumes of ammonium chloride ${\text{(NH}}_4\text{Cl})$ confirms the presence of sulphuric acid (${\text{H}}_2{\text{SO}}_4)$.

$Conc.H_{2}S{O}_4\left(aq\right)+NaCl\left(s\right)\to HCl\left(g\right)+NaHS{O}_4\left(aq\right)N{H}_3\left(g\right)+HCl\left(g\right)\to N{H}_{4}Cl\left(s\right)$


3. Barium sulphate test: A white precipitate of barium sulphate ${\text{(Ba}}_2{\text{SO}}_4)$
confirms the presence of sulphuric acid (${\text{H}}_2{\text{SO}}_4)$.

$BaC{l}_2\left(aq\right)+H_{2}S{O}_4\left(aq\right)\to BaS{O}_4(ppt.)$