Urea is to be crystallized from an aqueous solution that is 90% saturated at 100oC. If 90% of the urea is to be crystallized in the anhydrous form and the final solution temperature is to be 30oC, what fraction of the water must be evaporated?

NaCI crystals are to be produced from 1000 kg of a solution containing 10% NaCI. 1 % KOH and 89% water. The solution is first sent to an evaporator where 790 kg of water from the solution is removed. The hot concentrated solution is then sent to a crystallizer where the solution is cooled to 200C and NaCI crystals are precipitated. (No water evaporates). Each kg of crystals carries with it 0.1 kg of adhering mother liquor. The wet crystals are then treated in a drier where 95% of the water is removed. Make a complete material balance for the system. Data: solubility at 20°C is 36 g NaCI/100 g water. Assume that KOH is non-volatile and very soluble in water; its presence does not affect the solubility of NaCI in water.

For the reaction of decane with pure oxygen, if the fuel-to-oxygen ratio (by moles) is 0.05, determine the ratio of the actual fuel:oxygen ratio to the stoichiometric fuel:oxygen ratio; i.e. calculate the equivalence ratio. State, with an explanation. whether the mixture is rich or lean.

A 0.001 in. BCC iron foil is used to sepa- rate a high hydrogen content gas from a low hydrogen content gas at 650°C. 5 × 10% H atoms/cm³ are in equilibrium on one side of the foil, and 2 × 10³ H atoms/cm³ are in equilibrium on the other side. Determine (a) the concentration gradient of hydro- gen; and (b) the flux of hydrogen through the foil.