The important organic compound acetylene reacts with hydrogen in the presence of

Question

The important organic compound acetylene reacts with hydrogen in the presence of platinum metal catalyst to form ethane according to the equation

C2H2(g) + 2 H2(g) --> C2H6(g)

The pressure of a mixture of acetylene and an excess of hydrogen decreases from 0.100 atm to 0.042 atm in a vessel of a given volume after the platinum is introduced , and the temperature is restored to its initial value after the reaction reaches completion. What was the mole fraction of acetylene in the original mixture?

Explanation / Answer

C2H2(g) + 2H2(g) --> C2H6(g)

Let the partial pressure of C2H2 be 'x' atm

Thus, the partial pressure of H2 = 0.1-x atm

Now, H2 left unreacted = (0.1-x) - 2*x = 0.1-3x

Pressure of C2H6 = partial pressure of reacted C2H2 = x

Now, Pressure of the product = partial pressure of C2H6 + partial pressure of unreacted H2

or, 0.042 = x +0.1-3x

or, 2x = 0.058

or, x = 0.029 atm

Thus, mole fraction of C2H2 = partial pressure of C2H2/Total pressure of the gas mixture = 0.029/0.1 = 0.29

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