51.

Halogens are coloured and the colour deepens on moving down in the group from fluorine to iodine.

Explain why:

Hydride of sulphur is a gas while hydride of oxygen is a liquid.

Complete and balance the following reactions:

$$\begin{gathered} \left(1\right) \mathrm{NaCl} + {\mathrm{MnO}}_2 + {\mathrm{H}}_2{\mathrm{SO}}_4 \stackrel{ }{\to } \mathrm{\_\_\_} + \mathrm{\_\_\_\_}+\mathrm{\_\_\_\_} \\ \left(2\right) {\mathrm{KMnO}}_4 + {\mathrm{SO}}_2 + {\mathrm{H}}_2\mathrm{O} \stackrel{ }{\to } \mathrm{\_\_\_\_} + \mathrm{\_\_\_\_} + \mathrm{\_\_\_\_} \end{gathered}$$

Give balanced equations for the following reactions:

Benzaldehyde reacts with hydrazine.

Give balanced equations for the following reaction:

Acetic acid reacts with phosphorous pentachloride.

Give balanced equations for the following reaction:

Acetone reacts with sodium bisulphite.

Give one chemical test each to distinguish between the following pairs of compounds:

(1) Ethanol and acetic acid

(2) Acetaldehyde and benzaldehyde

Write chemical equations to illustrate the following name reactions:

Clemmensen’s reduction

Write chemical equations to illustrate the following name reactions:

Rosenmund’s reduction

Write chemical equations to illustrate the following name reactions:

HVZ reaction