For the gas phase reaction
`C_(2)H_(4)+H_(2) hArr C_(2)H_(6)(DeltaH=-32.7 "kcal")`
carried out in a vessel, the equilibrium concentration of `C_(2)H_(4)` can be increased by

Options

A. increasing the temperature
B. decreasing the pressure
C. removing some `H_(2)`
D. adding some `C_(2)H_(6)`

Explanation

`C_(2)H_(4) + H_(2) rarr C_(2)H_(6) , DeltaH = -32.7 kcal`
The above reaction is exothermic, increasing temperature will favour backward reaction, will increase the amount of `C_(2)H_(4)` . Decrease in pressure will favour reaction in direction containing more molecules (reactant side in the present case). Therefore, decreasing pressure will increase amount of `C_(2)H_(4)`.Removing `H_(2)` which is a reactant, will favour reaction in backwards direction, more `C_(2)H_(4)` will be formed. Adding `C_(2)H_(6)` will favour backward reaction and some of the `C_(2)H_(6)` will be dehydrogenated to `C_(2)H_(4)`.