Decreasing the concentration of a reactant in a chemical reaction affects the equilibrium position according to Le Chtelier's principle. Le Chtelier's principle states that if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will adjust its equilibrium position to counteract the change.When the concentration of a reactant is decreased, the equilibrium will shift to the side of the reactants to compensate for the decrease. This means that the reaction will proceed in the reverse direction to produce more reactants and consume products, ultimately re-establishing equilibrium.Let's consider the following reversible reaction as an example:N2 g + 3H2 g 2NH3 g In this reaction, nitrogen gas N2 reacts with hydrogen gas H2 to form ammonia gas NH3 . Suppose the reaction is at equilibrium, and we decrease the concentration of hydrogen gas H2 . According to Le Chtelier's principle, the equilibrium will shift to the side of the reactants left side to counteract the decrease in H2 concentration.As a result, the reaction will proceed in the reverse direction, consuming NH3 and producing more N2 and H2. This will continue until a new equilibrium position is established, with a lower concentration of NH3 and higher concentrations of N2 and H2 compared to the initial equilibrium state.