In any chemical reaction,equilibrium is supposed to be established when

$2 \ HI_{(g)} \rightleftharpoons H_{2(g)} + I_{2(g)}$
The equilibrium constant of the above reaction is $6.4$ at $300 \ K$. If $0.25 \ mol$ each of $H_{2}$ and $I_{2}$ are added to the system,the equilibrium constant will be

$A$ liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
$(a)$ What is the initial effect of the change on vapour pressure?
$(b)$ How do rates of evaporation and condensation change initially?
$(c)$ What happens when equilibrium is restored finally and what will be the final vapour pressure?

Assertion : The equilibrium constant is fixed and a characteristic for any given chemical reaction at a specified temperature.
Reason : The composition of the final equilibrium mixture at a particular temperature depends upon the starting amount of reactants.

For the equilibrium, $H_{2}O_{(l)} \rightleftharpoons H_{2}O_{(g)},$ which of the following is correct?

What is vapour pressure? Explain the statement: "In an open vessel,the rate of vaporization is constant,yet equilibrium is not established."