Consider the following reaction to produce hydrogen, done as a first step in the industrial process to make ammonia. Methane (from natural gas) reacts with steam over a nickel powder catalyst.
This reaction is done in a laboratory autoclave (a stainless steel pressure vessel) and allowed to reach equilibrium. More methane is then injected into the autoclave. We can predict that, when a new equilibrium is reached (at the same temperature), the concentration of every reagent in the equation will have increased, except that o
Only the concentration of methane will have increased, while the concentrations of steam and hydrogen will remain the same.
This is because the addition of more methane will push the reaction in the forward direction, according to Le Chatelier's principle. As a result, more methane will be converted to hydrogen, leading to an increase in the concentration of methane itself.
The concentrations of steam and hydrogen, on the other hand, will not change because they are involved in the equilibrium reaction. Increasing the concentration of methane does not affect the equilibrium concentrations of these species.