question_answer

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

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

Answer:

(i) Quicklime (CaO) reacts vigorously with water to form slaked lime \[[Ca{{(OH)}_{2}}]\] which is white in colour.

\[\underset{\begin{smallmatrix}  \text{Calcium oxide} \\  \text{(Quick lime)} \end{smallmatrix}}{\mathop{CaO(s)}}\,\mathrm{ }+\mathrm{ }{{H}_{2}}O(l)\xrightarrow{\text{Combination}}\underset{\begin{smallmatrix}  \text{Calcium hydroxide} \\  \text{(Slaked lime)(white)} \end{smallmatrix}}{\mathop{Ca{{(OH)}_{2}}(s)}}\,\]

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

\[\underset{\begin{smallmatrix}  \text{Ferrous Sulphate} \\  \text{(green colour)} \end{smallmatrix}}{\mathop{2FeS{{O}_{4}}(s)}}\,\xrightarrow[\text{Decomposition}]{\Delta }\underset{\begin{smallmatrix}  \text{Ferric oxide} \\  \text{(brown)} \end{smallmatrix}}{\mathop{F{{e}_{2}}{{O}_{3}}(s)}}\,+S{{O}_{2}}(g)+S{{O}_{3}}(g)\]