The reaction
2 so2(g) + o2(g)< --> 2 so3(g)
has an equilibrium expression. the mass action expression
forconcentration of oxygen has an exponent of

The mass action expression  for concentration of oxygen has an exponent of one.

Explanation:

2 SO₂(g) + O₂(g) ⇄ 2 SO₃(g)

This is the expression for Kc:

Kc = [SO₃]² / [O₂] . [SO₂]²

The mass action expression has a totally relation with stoichiometry.

the atomic mass is the bottom number on the element.

-steel jelly

i think its 5049.

i hope this !