The addition of a small amount of argon at a constant volume will not affect the equilibrium of the following reaction:

1. H2(g)+I2(g)⇌2HI(g)
2. PCl5(g)⇌ PCl3(g)+Cl2(g)
3. N2(g)+3H2(g)⇌2NH3(g)
4. The equilibrium will remain unaffected in all the three cases.