Question

31. (i) (a) A solution is prepared by dissolving 15g of sodium chloride in 200g of water. What is the
mass by mass percentage of NaCl in the solution?
(b) What is solute and solvent in aerated drinks?
(c) Given a solution of substance A. How will you test whether it is a saturated or unsaturated
Solution with respect to A at the given temperature.
(ii) Write any two applications of chromatography. Also write a condition necessary for
Chromatography.

Answer 1

Answer:

Total weight of solution = weight of solute + weight of solvent : (15 + 200)g = 215g

Weight of solute = 15g

So, %w/w = 15/215 = 6.976% or approx 7% w/w

If you were doing % w/v :

Assuming the addition of salt DOES NOT INCREASE SOLUTION VOLUME :

15g/200ml = 7.5% w/v

But this doesn’t hold true, as adding salt to water will increase the volume, but not by 1ml for 1g (more like 1ml for every 2g)

If you were doing this properly :

15g made up to 200ml with water = 7.5% w/v

15g mixed with 200ml of water will be slightly less %w/v, as the total volume will be slightly more than 200ml, so probably more like 7.2 %w/v.