Question

suppose you prepare 500ml of a solution of salt and let it to sit out uncovered, for several days and some of the water evaporates. does the concentrattion of the solution left in the container increase, decrease or same the same?

Answer 1

The concentration of any soution is dependent on the volume of solvent present in solution. As 500 ml of solution will have a fixed concentration (which depends upon how much solute present in this) initially. After keeping it for sevaral days (uncovered), possibilty of evaporation of solvent from solution is possible which in turn leads to the decrease in total volume of solution. The volume term is inversely proportional to the concentration of solution (either in terms of normality, molarity or molality). Hence, the concentrattion of the solution left in the container would increase.