Question

1) The equilibrium constant Kc of the reaction
A + B ⇄ C + D is equal to 9.
If 0.4 mol of A and 0.4 mol of B are reacted, the number of moles of D formed is:
a) 0.30
b) 0.60
c) 0.40
d) 0.36
e) 0.18

Answer 1

Answer:

a) 0.30

Explanation:

Kc = [C] [D] / ([A] [B])

Set up an ICE table:

$\left[\begin{array}{cccc}&Initial&Change&Equilibrium\\A&0.4&-x&0.4-x\\B&0.4&-x&0.4-x\\C&0&+x&x\\D&0&+x&x\end{array}\right]$

Plug in values and solve:

9 = x² / (0.4 − x)²

3 = x / (0.4 − x)

1.2 − 3x = x

1.2 = 4x

x = 0.3