A seashore sand mixture contains 85% insoluble sand, 12% salt, and 3% water by weight. 100...

Transcribed Image Text:

A seashore sand mixture contains 85% insoluble sand, 12% salt, and 3% water by weight. 100 kilograms of this mixture is to be washed by batch operations so that it will contain less than 0.2% salt after drying. In each washing, the sand mixture is mixed with 200 kilograms of water and the resulting saline solution is discarded. The sand mixture retains 0.5 kilograms of water per kilogram of insoluble sand after each washing. Note that the mixture is not dried between washings. (a) How many washings with 200-kg batches of water are required to give the desired purity of the sand? (b) Derive a general expression for the weight fraction of salt in the dried mixture after N washings. Note that the solubility of salt in water is 35.7 kg salt per 100 kg of water. A seashore sand mixture contains 85% insoluble sand, 12% salt, and 3% water by weight. 100 kilograms of this mixture is to be washed by batch operations so that it will contain less than 0.2% salt after drying. In each washing, the sand mixture is mixed with 200 kilograms of water and the resulting saline solution is discarded. The sand mixture retains 0.5 kilograms of water per kilogram of insoluble sand after each washing. Note that the mixture is not dried between washings. (a) How many washings with 200-kg batches of water are required to give the desired purity of the sand? (b) Derive a general expression for the weight fraction of salt in the dried mixture after N washings. Note that the solubility of salt in water is 35.7 kg salt per 100 kg of water.

Answer rating: 100% (QA)

Lets denote S as the weight of salt in the mixture before washing W as the weight of water added in ... View the full answer