Aliquid-process feed stream contains 99 mol-% of species 1 and 1 mol-% of impurity, species 2. the impurity level is to be reduced to 0.1 mol-% by contacting the feed stream with a stream of pure liquid solvent, species 3, in a mixer-settler. species 1 and 3 are essentially immiscible. owing to “good chemistry”, it is expected that species 2 will selectively concentrate in the solvent phase. (a) what is the mole fraction x2 of the impurity in the solvent phase leaving the mixersettler? (b) determine the required moles of solvent ns per mole of feed.