On increasing pressure, equilibrium shifts towards lesser number of gaseous moles. It means gaseous moles on product are less than gaseous moles on reactant side, i.e. ∆ng<0. (i) X2(g)+3Y2(g)⇌2XY3(g);∆ng=2−4=−2 (ii) X2(g)+Y2(g)⇌2XY(g);∆ng=2−2=0 (iii) X2(g)+Z2(g)⇌2XZ(g);∆ng=2−2=0 (iv) X2(g)+Y4(g)⇌2XY2(g);∆ng=2−2=0 ∆ng<0 only for reaction (i) hence, position of equilibrium shifts towards the products if total pressure is increased.