Question

(i) In the combination reaction of adding water to quick lime, name the product formed and write its colour.

(ii) While studying the decompostion reaction, by heating anhydrous ferrous sulphate crystals in a test-tube, a product is formed in the test-tube. Name the product and write its colour.

Answer 1

(i) Quicklime $\left(CaO\right)$ reacts vigorously with water to form slaked lime $\left[Ca\right(OH{)}_2]$, which is white in colour.
$\begin{array}{ccc}& & \\ CaO\left(s\right)+H_{2}O\left(l\right)& \to & Ca\left(OH{)}_2\right(s)\\ \text{Calcium oxide}& & \text{Calcium hydroxide}\\ \text{(Quich lime)}& & \text{(Slaked lime)(white)}\end{array}$

(ii) When anhydrous ferrous sulphate is heated strongly, it decomposes to form brown coloured ferric oxide along with sulphur dioxide and sulphur trioxide gases.

$\begin{array}{ccc}& & \\ 2FeS{O}_4\left(s\right)& \stackrel{\Delta }{\to }& F{e}_2{O}_3\left(s\right)+S{O}_2\left(g\right)+S{O}_3\left(g\right)\\ \text{Ferrous sulphate}& & \text{Ferric oxide}\\ \text{(white colour)}& & \text{(brown)}\end{array}$