the balanced equation for the above reaction is as follows;
5 C (s) + 2 SO₂ (g) --> CS₂ (l) + 4 CO (g)
stoichiometry of C to CS₂ formed is 5:1
5 mol of C react to form 1 mol of CS₂
1 mol of C form - 1/5 mol of CS₂
therefore when 2.79 mol of C react - 1/5 x 2.79
number of CS₂ moles formed - 0.56 mol