Chapter 15, Problem 88E

The equilibrium constant for the reaction ${\text{SO}}_{\text{2}}\left(\text{g}\right)+{\text{NO}}_{\text{2}}\left(\text{g}\right)\rightleftharpoons {\text{SO}}_{\text{3}}\left(\text{g}\right)\text{+NO}\left(\text{g}\right)$ is 30. Find the amount of NO₂ that must be added to 2.4 mol of SO₂ in order to form 1.2 mol of SO₃ at equilibrium.