Hydrogen gas at a pressure of 1.25 bar is contained in a thick-walled neoprene rubber sphere which has inner and outer radii of 70mm and 80mm, respectively. The concentration of hydrogen at the outer surface of the sphere is negligible and leakage is so small that steady-state conditions can be assumed to occur for a long time. The solubility of hydrogen in rubber is 2.37 x 10-3 kmolm -3 (bar)-1 and the diffusivity is 1.8 x 10 -10 m2 s-1. Calculate the rate at which hydrogen escapes fromthe sphere. (Assume the inner surface of rubber is saturated with hydrogen).