Question

For the chemical equation SO 2 ( g ) + NO 2 ( g ) − ⇀ ↽ − SO 3 ( g ) + NO ( g ) SO2(g)+NO2(g)↽−−⇀SO3(g)+NO(g) the equilibrium constant at a certain temperature is 2.70 . 2.70. At this temperature, calculate the number of moles of NO 2 ( g ) NO2(g) that must be added to 2.99 mol SO 2 ( g ) 2.99 mol SO2(g) in order to form 1.30 mol SO 3 ( g ) 1.30 mol SO3(g) at equilibrium.

Answer 1

Answer : The number of moles of $NO_2$ added must be, 0.37 mol

Explanation :

The given chemical reaction is:

                      $SO_2(g)+NO_2(g)\rightleftharpoons SO_3(g)+NO(g)$

Initial mol.     2.99           x                 0           0

At eqm.      (2.99-1.30)  (x-1.30)         1.30       1.30

                      = 1.69

The expression for equilibrium constant is:

$K_c=\frac{[SO_3][NO]}{[SO_2][NO_2]}$

Now put all the given values in this expression, we get:

$2.70=\frac{(1.30)\times (1.30)}{(1.69)\times (x-1.30)}$

x  = 1.67 mol

The moles of $NO_2$ added = (x-1.30) = (1.67-1.30) = 0.37 mol