A 5.00 mol sample of solid A was placed in a sealed 1.00 L container and allowed to decompose into gaseous B and C.

Question

The concentration of B steadily increased until it reached 1.40 M, where it remained constant.

A(s)↽−−⇀B(g)+C(g)

Then, the container volume was doubled and equilibrium was re‑established. How many moles of A remain?

Answer 1

A -----> B + C M = mol / V mole = MV mol A = 5

mol B at equilibrium = 1.4 mol/L x 2 L = 2.8 mol

A -----> B + C

I 5 mol 0 0

C -2.8 +2.8 +2.8

E 2.2 2.8 2.8 mole A at equilibrium = 2.20 moles