In which of the following reactions, the equiLiBrium remains uNaFfected on addition of a small amount of argon at constant volume?
1) N2(g) + 3H2(g) ⇌ 2NH₃(g)
2) 2SO₂(g) + O2(g) ⇌ 2SO₃(g)
3) 2H2(g) + O2(g) ⇌ 2H₂O(g)
4) 2NO(g) + O2(g) ⇌ 2NO₂(g)