An increase in pressure will favour the forward reaction (production of NH\(_4\)Cl).

According to Le Chatelier's principle, increasing the pressure on a system at equilibrium will cause the equilibrium to shift in the direction that reduces the total number of moles of gas. In this reaction, the reactant side has two moles of gas (one NH\(_3\) and one HCl), while the product side has zero moles of gas (solid NH\(_4\)Cl). The system relieves the pressure by favoring the side with fewer gas molecules, thus promoting the formation of the solid product.

NH\(_3\) + HCl ⇌ NH\(_4\)Cl

An increase in pressure will favour the forward reaction (production of NH\(_4\)Cl).