Consider the reaction: ${\mathrm{N}}_2\left(g\right)+3{\mathrm{H}}_2\left(g\right)\rightleftharpoons 2{\mathrm{NH}}_3\left(g\right)$ (exothermic process)

How many of given changes will result in decrease in number of moles of ${\mathrm{N}}_2$ gas initially present at equilibrium in a closed vessel?

1. Increase in temperature
2. Decrease in volume of container
3. Increase in total pressure
4. Addition of $\mathrm{He}$ gas at constant pressure
5. Addition of $\mathrm{He}$ gas at constant volume
6. Addition of small amount of${\mathrm{H}}_2\mathrm{O}$ (l) in vessel
7. Addition of ${\mathrm{H}}_2$ gas in vessel at constant volume
8. Removing some moles of ${\mathrm{NH}}_3$
9. Addition of ${\mathrm{N}}_2$ gas