Question

Absorption is accompanied by the evolution of heat. So, according to Le-Chatelier principle, the amount of substance adsorbed should:
A. Increase with decrease in temperature
B. Increase with increase in temperature
C. Decrease with decrease in temperature
D. Decrease with increase in temperature

Answer 1

We will use the Le-Chatelier principle. Le-Chatlier principle tells the effect of change on equilibrium of a reaction. First we will determine that the given reaction is exothermic or endothermic. Exothermic reaction goes in forward direction on decreasing temperature and endothermic reaction goes in forward direction on increasing temperature.

Complete answer:

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.
Effect of temperature: It depends upon the type of reaction on the basis of heat. If during the reaction heat evolves, the reaction is known as exothermic reaction. If during the reaction heat absorbed, the reaction is known as endothermic.
In exothermic reactions, heat evolves so, these reactions take place at low temperature so, decrease in temperature favour the reaction in forward direction.
In endothermic reactions, heat is absorbed, so these reactions take place at high temperatures, so increases in temperature favour the reaction in a forward direction.
It is given that reaction is accompanied by the evolution of heat means the reaction is exothermic so, according to Le-Chatelier principle, the amount of substance adsorbed should increase with decrease in temperature.

Therefore, option (A) Increase with decrease in temperature, is correct.

Note: As the reaction goes in forward direction, the consumption of reactant increases. So, the amount of substance absorbed increases. Increased concentration of product always favours the reaction in a backward direction. The high temperature favors the endothermic reaction and low-temperature favour the exothermic reaction. On increasing pressure the reaction goes in that direction lesser number moles of gaseous species a represent.