Question

A student prepared a homogeneous solution by
dissolving 65 g ammonium chloride in 185 g water
and stored it in beaker 'A'. Another student took
th solution from this beaker 'A' and stored it in
another beaker 'B'. The amount of water that should
be added to the beaker 'B' to make its concentration
20% (w/w) is​

Answer 1

The amount of water that should be added to the solution to make its concentration 20% (W/W) is 6 ml.

• % (W/W) = Weight of solute in 100 g of solution
• For solution A:

                 250 g of solution has 185 g of water

Therefore, 100 g of solution will have 185 * 100/250 = 74 g of water

• For a concentration of 20% W/W, the weight of solvent should be 80 g.
• Amount of water to be added = 80 - 74 = 6 g = 6 ml (Density of water = 1g/ml)