In a catalytic reaction involving the formation of ammonia by Haber's process N2+3H2 → 2NH3, the rate of appearance of NH3 was measured as 2.5 x 10-4 mol L-1S-1 The rate of disappearance of H2 will be
N2+3H2 → 2NH3,
-1/3dH2/dt = -1/2dNH3/dt
-dH2/dt = 1/2x3x2.5x10-4
-dH2/dt = 3.75 x 10-4 mol L-1S-1