Question

How is Le-chatelier's principle useful in the chemistry industry? What is the effect of temperature on equilibrium constant?

Answer 1

To determine the use and effect of temperature on equilibrium constant we should know the Le-chatlier principle and equilibrium constant. According to the Le-chatlier principle if a reaction equilibrium is disturbed by changing the variable such as temperature, pressure number of mole, the reaction goes in that direction where the effect of change can be cancelled out.

Complete step-by-step answer: The process which absorbs heat during the reaction and decreases the temperature of the surrounding is known as the endothermic process. The process which releases heat during the reaction and increases the temperature of the surrounding is known as an exothermic process.
Effect of temperature: Endothermic reaction requires heat to occur so, on increasing temperature equilibrium shifts in the forward direction, and thus the value of equilibrium constant increases. Exothermic reactions release heat so, on increasing temperature equilibrium shifts in a backward direction, so the value of the equilibrium constant decreases.
To understand the effect of temperature on equilibrium constant according to the Le-chatlier principle, let’s consider a very famous industrial process for the preparation of ammonia.
Ammonia is prepared by a reaction of hydrogen and nitrogen in presence of a catalyst.${{\text{N}}_{\text{2}}}\,\,{\text{ + }}\,{\text{3}}{{\text{H}}_2}\,\mathop \to \limits^{{\text{Fe}}} {\text{2N}}{{\text{H}}_{\text{3}}}\,{\text{ + }}\,{\text{\Delta }}$
Equilibrium constant for the reaction is as follows:
${{\text{K}}_{{\text{eq}}}}\,{\text{ = }}\,\dfrac{{{{{\text{[N}}{{\text{H}}_{\text{3}}}{\text{]}}}^{\text{2}}}}}{{{\text{[}}{{\text{N}}_{\text{2}}}{\text{][}}{{\text{H}}_{\text{2}}}{{\text{]}}^{\text{3}}}}}$
During the preparation of ammonia, heat is released, so the temperature of the reaction increases, so cooling is used when nitrogen and hydrogen are passed over the catalyst. Room temperature favours the equilibrium constant in the forward direction. To obtain a high yield of ammonia temperature is maintained near room temperature.
On increasing the temperature, product ammonia will consume heat and form nitrogen and hydrogen so the equilibrium constant decreases.
in decreasing the temperature, the reactant releases the heat and forms ammonia so the equilibrium constant increases because the equilibrium constant is directly proportional to the ammonia concentration.
Therefore, the Le-chatlier principle is useful in the chemistry industry to determine the favourable conditions of temperature and pressure for a reaction. The effect of temperature on equilibrium constant depends upon whether the reaction is endothermic or exothermic.

Note: In endothermic reactions, on increasing temperature the rate of forward direction increases and thus rate of reverse direction decreases so equilibrium constant increases. In exothermic reactions, on increasing temperature the rate of forward direction decreases, and thus the rate of reverse direction increases so the equilibrium constant decreases. The high temperature favours the endothermic reaction and the low-temperature favours the exothermic reaction.