Question

For the equilibrium Br2 + Cl2 goes to 2BrCl at 400 K ,Kc = 7.0. 0.30 of Br2 and 0.30 of Cl2 are introduced into a 1.0 L- container at 400 K.a) What will be the equilibrium concentration of Br2? b) What will be the equilibrium concentration of Cl2 ? c) What will be the equilibrium concentration of BrCl?

Answer 1

0.30 WHAT of Br2 and 0.30 WHAT of Cl2 are introduced........ I suspect you meant moles and the following answer is based on that assumption.
0.30 moles/1 L = 0.30M for (Br2) and (Cl2) initially. Set up and ICE chart.

............Br2 + Cl2 ==> 2BrCl
initial...0.30M...0.30M.....0
change......-x....-x........2x
equil.....0.30-x..0.30-x....2x

Substitute the equilibrium values into the Kc expression and solve for x. From that you can calculate (Br2), (Cl2) and (BrCl) at equilibrium.