Following reaction arise between Br2 and Cl2
Br2 + Cl2 → 2BrCl
(1mole) (1mole) (2moles)
From above balanced reaction, it can be seen that 1 mole of Br2 reacts with 1 mole of Cl2 to form 2 mole of BrCl
Thus, when 2.74 mol Cl2 reacts with excess Br2, 2.74 X 2 = 5.48 moles of BrCl will be formed.