Ethylene, C_2H_4, used to make polyethylene plastics, can be made from ethane, C

Question

Ethylene, C_2H_4, used to make polyethylene plastics, can be made from ethane, C_2H_6, one of the components of natural gas. The heat of reaction for the decomposition of ethane gas into ethylene gas and hydrogen gas is 136.94 kJ per mole of C_2H_4 formed, so it is endothermic. The reaction is run at high temperature, in part because at 800-900 degree C, the equilibrium constant for the reaction is much higher, indicating that a higher percentage of products forms at this temperature. Explain why increased temperature drives this reversible chemical reaction in the endergonic direction and why this leads to an increase in the equilibrium constant for the reaction. C_2H_6(g) C_2H_4(g) + H_2(g)

Explanation / Answer

C2H6 --> C2H4 + H2 + del(H)
where del(H) is the heat absorbed. So it is an endothermic reaction.
The reaction of the system is around 800-900 C.
If we increase the temperature of the surrounding, the reaction will try to absorb that extra heat from an increase in temperature. So the reaction will go in the forward direction i.e. formation of Ethylene C2H4.

This is also stated according to Le Chatelier's principle, that an increase in temperature favors the endothermic reaction and vice versa.

Initially, the equilibrium constant is = ([C2H4] * [H2]) / ([C2H6])
With an increase in temperature, there will be forward reaction leading to more formation of C2H4 and H2, thus increasing the concentration of products. Thereby the Equilibrium constant will increase according to the formula.

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