Density of some aq. solution (60% by wt.) is lowered upto 1.2 gm/cc by
addition of water. If initial density was 1.6 gm/cc then new approximate
percentage by wt. will be (Take density of water = 1 gm/cc)
Answers
new approximate percentage by weight will be 26.67 %.
It has given that the density of some aqueous solution (60% by Wt.) is lowered upto 1.2 g/cc by addition of water. initial density of solution was 1.6 g/cc
then we have to find new approximate percentage by Wt.
In 100 ml of solution 60% of solute by weight.
weight of solution = 100ml × 1.6 g/ml = 160g
now weight of solute = 60% of 160 = 60 × 160/100 = 96g
let x g of water is added to the solution.
new weight of solution = (160 + x)g .....(1)
new volume of solution = (100 + x) ml
now weight of solution = volume of solution × new density of solution.
= (100 + x)ml × 1.2 g/ml = (120 + 1.2x ) g .....(2)
on comparing equations (1) and (2) we get,
160 + x = 120 + 1.2x
⇒40 = 0.2x
⇒x = 200g
percentage by weight of solution = weight of solution/mass of solution × 100
= 96/(160 + 200) × 100
= 960/36
= 26.67 %
therefore new approximate percentage by weight will be 26.67 %