(N/A) The effect of temperature on equilibrium can be demonstrated by taking $NO_{2}$ gas (brown in colour) which dimerises into $N_{2}O_{4}$ gas (colourless).
$2NO_{2(g)} \rightleftharpoons N_{2}O_{4(g)}$; $\Delta H = -57.2 \ kJ \ mol^{-1}$
(Brown colour gas) $\quad$ (Colourless gas)
Method of experiment: $NO_{2}$ gas,prepared by the addition of $Cu$ turnings to concentrated $HNO_{3}$,is collected in two $5 \ mL$ test tubes (ensuring the same intensity of colour of gas in each tube) and the stoppers are sealed with araldite. Take three $250 \ mL$ beakers labeled $1$,$2$,and $3$.
Beaker $1$ contains a freezing mixture $(270 \ K)$,beaker $2$ contains water at room temperature $(298 \ K)$,and beaker $3$ contains hot water $(363 \ K)$.
Both test tubes are placed in beaker $2$ for $8-10$ minutes to reach equilibrium. After this,one tube is placed in beaker $1$ and the other in beaker $3$. The effect of temperature on the direction of the reaction is observed.
Observation:
$(i)$ At low temperature in beaker $1$ $(270 \ K)$,the forward reaction (formation of $N_{2}O_{4}$) is favoured because the reaction is exothermic. Thus,the intensity of the brown colour due to $NO_{2}$ decreases.
$(ii)$ In beaker $3$ $(363 \ K)$,the high temperature favours the reverse reaction (formation of $NO_{2}$),and thus,the brown colour intensifies.
Deduction: In an exothermic reaction,a decrease in temperature shifts the equilibrium in the forward direction,while an increase in temperature shifts it in the reverse direction.