Kp= 0.04 atm at 899 K for the equilibrium shown below. What is the equilibrium concentration of C2H6 when it is placed in a flask at 4.0 atm pressure and allowed to come to equilibrium?

C2H6 (g) ⇌ C2H4 (g) + H2 (g)

For the given reaction, lets assume that p atm is the pressure exerted by ethene and hydrogen gas at equilibrium.

Therefore, the given reaction is:


C2H6 (g) ⇌ C2H4 (g) + H2 (g)



Equilibrium pressure constant (Kp) is defined as a number that expresses the relationship between the partial pressures of products and reactants present at equilibrium in a reversible chemical reaction at a given temperature.


Here. Kp= 0.04 atm


For the given reaction,



Where, = partial pressure pf C2H4 in atom at equilibrium


= partial pressure of H2 in atom at equilibrium


= partial pressure of C2H6 in atom at equilibrium



p2=0.16-0.04p


p2+0.04p-0.16=0


Now,



(Taking positive value)


p=0.38


Therefore at equilibrium, [C2H6]= 4 - p = 4 - 0.38


=3.62 atom


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