80 kg of Na_{2}SO_{4} (molecular weight = 142) is present in 330 kg of an aqueous solution. The solution is cooled such that. 80 kg of Na_{2}SO_{4} .10H_{2}O crystals separate out. The weight fraction of Na_{2}SO_{4} in the remaining solution is

A butane isomerisation process produces 70 kmole/hr of pure isobutane. A purge stream removed continuously, contains 85% n-butane and 15% impurity (mole%). The feed stream is n-butane containing 1% impurity (mole%). The flow rate of the purge stream will be

"The equilibrium value of the mole fraction of the gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid surface". This statement pertaining to the solubility of gases in liquid is the __________ law.