Question

State one appropriate observation: conc. sulphuric acid is added dropwise to a crystal of copper sulphate.

Answer 1

1. $\mathrm{conc}.{\mathrm{H}}_2{\mathrm{SO}}_4$ acts as a dehydrating agent. i.e. it removes water of crystallization from the crystal of ${\mathrm{CuSO}}_4·5{\mathrm{H}}_2\mathrm{O}$
2. $\mathrm{conc}.{\mathrm{H}}_2{\mathrm{SO}}_4$ is added slowly to the crystal of ${\mathrm{CuSO}}_4·5{\mathrm{H}}_2\mathrm{O}$ to observe the crystalline ${\mathrm{H}}_2\mathrm{O}$
3. A white precipitate ${\mathrm{CuSO}}_4$ is formed.
4. $$\begin{gathered} {\mathrm{CuSO}}_4·5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)\stackrel{\mathrm{conc}.{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }{\mathrm{CuSO}}_4\left(\mathrm{s}\right)+5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{copper}\mathrm{sulphate}\mathrm{pentahydrate}\stackrel{\mathrm{conc}.{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }\mathrm{copper}\mathrm{sulphate}+\mathrm{water} \end{gathered}$$