Question

Consider the reaction,
$2NO\left(g\right)+2H_2\left(g\right)=N_2\left(g\right)+2H_{2}O\left(g\right)$.
In the above reaction, by what factor would the reaction quotient change if the concentration of $NO$ was doubled?

• A. $\frac{1}{4}$
• B. 2
• C. $\frac{1}{2}$
• D. No change

Answer 1

The correct option is A $\frac{1}{4}$

We can find the reaction quotient equation for our reaction by substituting the variables.
$2N{O}_{\left(g\right)}+2H_{2\left(g\right)}\rightleftharpoons N_{2\left(g\right)}+2H_{2}O\left(g\right)$
$Q_1=\frac{\left[N_2\right][H_{2}O{]}^2}{\left[NO{]}^2\right[H_2{]}^2}$
Concentration of NO is squared. so doubling the concentration of NO changes the reaction quotient by a factor of one - fourth
$Q_2=\frac{\left[N_2\right][H_{2}O{]}^2}{\left[2NO{]}^2\right[H_2{]}^2}=\frac{\left[N_2\right][H_{2}O{]}^2}{4\left[NO{]}^2\right[H_2{]}^2}$
$Q_2=\frac{1}{4}{Q}_1$