Question

4.5 moles of each hydrogen and iodine are heated in a sealed 10-liter vessel. At equilibrium, 3 moles of hydrogen iodide was found.

The equilibrium constant for $H_2\left(g\right)$ + $I_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$ is;

• A. 1
• B. 10
• C. 5
• D. 0.33

Answer 1

The correct option is A 1

The equilibrium reaction is $H_2\left(g\right)+I_2\left(g\right)\iff 2HI\left(g\right)$.

The number of moles of various species present initially and at equilibrium is given in the following table.

	$H_2$	$I_2$	$HI$
Initial	4.5	4.5	0
Change	1.5	1.5	3.0
Equilibrium	3.0	3.0	3.0

The expression for the equilibrium constant is $K_c=\frac{[HI{]}^2}{\left[H_2\right]\left[I_2\right]}$.

Substitute values in the above expression.

$K_c=\frac{(\frac{3.0}{10}{)}^2}{\left(\frac{3.0}{10}\right)\times \left(\frac{3.0}{10}\right)}=1$

So, the correct option is $A$