If the concentration of reactants is increased by $x$ times,the equilibrium constant $K$ will become ................

In which of the following cases does the reaction go farthest to completion?

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 reaction $H_{2(g)} + I_{2(g)} \rightleftharpoons 2HI_{(g)}$,the equilibrium constant changes with:

$2 \ HI_{(g)} \rightleftharpoons H_{2(g)} + I_{2(g)}$
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

In the reversible reaction,a catalyst is the substance which: