Question

The effect of addition of helium gas to the following reaction in equilibrium state, is : $PCl ( g ) \rightleftharpoons PCl _3( g )+ Cl _2( g )$

• A. addition of helium will not affect the equilibrium.
• B. the equilibrium will shift in the forward direction and more of $Cl _2$ and $PCl _3$ gases will be produced.
• C. the equilibrium will go backward due to suppression of dissociation of $PCl _5$.
• D. helium will deactivate $PCl _5$ and reaction will stop.

Answer 1

Answer: (B)

$PCl ( g ) \rightleftharpoons PCl _3( g )+ Cl _2( g )$
(Case 1 : At constant $P$ - volume will increase so reaction will shift in forward direction then answer will be $A$
Case 2 : At constant volume no change in active mass so reaction will not shift in any direction then answer will be D.