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Question: The reaction, \({C_2}{H_4}(g) + {H_2}(g) \rightleftarrows {C_2}{H_6}(g);\Delta H = - 32.7kcal\) i...

The reaction,
C2H4(g)+H2(g)⇄C2H6(g);ΔH=−32.7kcal{C_2}{H_4}(g) + {H_2}(g) \rightleftarrows {C_2}{H_6}(g);\Delta H = - 32.7kcal is carried out in a vessel. The equilibrium concentration of C2H4{C_2}{H_4} can be increased by :
A. increasing temperature
B. Decreasing the pressure
C. Removing some hydrogen
D. All of the above

Explanation

Solution

By analysing the given question we can understand that the above reaction is an exothermic reaction that means it is releasing heat in the product side. The negative value of enthalpy indicates that the reaction is exothermic .The number of molecules in the reactant side is more than the product side. We will use the Le Chatelier principle to solve the question.

Complete answer:
According to the Le Chatelier principle if we increase the temperature of an exothermic reaction the reaction will proceed in the backward direction to nullify the effect of increasing the temperature. That means it will shift to the reactant side, thus increasing the concentration of C2H4{C_2}{H_4} in the reactant side. The number of moles of gaseous species in the reactant side is more than that of the product side. So if we decrease the pressure the equilibrium will shift towards the reactant side , thus it will increase the concentration of ethene. Now if we remove some hydrogen from reactant side , the equilibrium will shift to reactant side so that more C2H6{C_2}{H_6} is converted to C2H4{C_2}{H_4} and H2{H_2} . So from the above explanation it is clear that increasing the temperature, decreasing the pressure and removing some hydrogen will increase the concentration of ethene in the reactant side.

The correct answer of the above question is, D

Additional information: Le Chatelier principle is also known as equilibrium law. It states that whenever the chemical equilibrium is disturbed , it tends to oppose the change to nullify the effect of the change.

Note: Whenever we increase temperature in an exothermic reaction the equilibrium shifts towards reactant side and whenever we increase the temperature in endothermic reaction the equilibrium shifts towards the product side. Always use Le Chatelier's principle if the chemical reaction is subjected to change in volume, pressure, temperature or number of moles of the reactant or products.