Question

Match the following reactions with their observations.

• A. White precipitate
• B. Exothermic
• C. Black precipitate

Answer 1

When any sulphate salt reacts with barium chloride it forms a thick white precipitate of barium chloride. The reaction involvesd is:

${\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+{\mathrm{BaCl}}_2\left(\mathrm{aq}\right)\to {\mathrm{BaSO}}_4\left(s\right)+2\mathrm{NaCl}\left(\mathrm{aq}\right)$

Dilution of $H_2{\mathrm{SO}}_4$ is an exothermic reaction. The reaction is as follows:

$H_2{\mathrm{SO}}_4\left(l\right)+H_{2}O\left(l\right)\to H^{+}\left(\mathrm{aq}\right)+{\mathrm{HSO}}_4\left(\mathrm{aq}\right)+\mathrm{Heat}$

On treating glucose with sulphuric acid it gets dehydrated and forms a charred precipitate of carbon black.
$C_6{H}_{12}{O}_6\left(s\right)\stackrel{H_2{\mathrm{SO}}_4}{\to }6C+5H_{2}O$