What happens when (write chemical equation in each case) (a) ethanol is burnt in air ? (b) ethanol is heated with excess conc. $H_2SO_4$ at 443 K ? (c) a piece of sodium is dropped into ethanol ?

The chemical reactions and observations for each case are as follows:

(a) Ethanol is burnt in air:

Ethanol burns readily in the presence of oxygen (air) with a clear, blue flame to undergo complete combustion, producing carbon dioxide gas, water vapor, heat, and light.

$$\text{Chemical Equation: } C_2H_5OH + 3O_2 \rightarrow 2CO_2 + 3H_2O + \text{Heat and Light}$$

(b) Ethanol is heated with excess conc. $H_2SO_4$ at 443 K:

Heating ethanol at $443\text{ K}$ with excess concentrated sulphuric acid results in the dehydration of ethanol to form ethene (an unsaturated hydrocarbon) and water. In this reaction, concentrated sulphuric acid acts as a dehydrating agent because it removes water from ethanol.

$$\text{Chemical Equation: } CH_3-CH_2OH \xrightarrow{\text{Hot conc. } H_2SO_4, 443\text{ K}} CH_2=CH_2 + H_2O$$

(c) A piece of sodium is dropped into ethanol:

Ethanol reacts with sodium metal at room temperature to form sodium ethoxide with the rapid evolution of hydrogen gas (which can be tested with a burning splinter, producing a characteristic 'pop' sound).

$$\text{Chemical Equation: } 2CH_3CH_2OH + 2Na \rightarrow 2CH_3CH_2ONa + H_2 \uparrow$$