For any reversible reaction,if the concentration of the reactant increases,what is the effect on the equilibrium constant?

If some $He$ gas is added to the equilibrium $PCl_{5(g)} \rightleftharpoons PCl_{3(g)} + Cl_{2(g)}$ at constant pressure and temperature,the equilibrium constant of the reaction will....

In the given reaction $N_2 + O_2 \rightleftharpoons 2NO$,equilibrium means that

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

For the reaction $A + B \rightleftharpoons C + D$,the equilibrium constant is $K$. If the initial moles of $A$ and $B$ are $1.0 \ mol$ each,what will be the value of the equilibrium constant in a second experiment under the same conditions if the initial moles of $A$ and $B$ are $2 \ mol$ and $3 \ mol$ respectively?

Which of the following nitrogen oxides is the most stable?