Question

1. How many grams of salt should be added to 60 g water so that 25% w/w solution can be
obtained?
​

Answer 1

Answer:

Let weight of solute be x and weight of solvent be y.

Formula for W/W solution:

\begin{gathered} \frac{x}{x + y} \times 100 \\ = > \frac{x}{x + 60} \times 100 = 15 \\ = > x = \frac{15}{100} \times (x + 60) \\ = > x = \frac{3}{20} (x + 60) \\ = > x = \frac{3}{20} x + \frac{3}{20} \times 60 \\ = > x - \frac{3}{20} x= 3 \times 3 \\ = > \frac{20 - 3}{20}x = 9 \\ = > \frac{17}{20} x = 9 \\ = > x = 9 \times \frac{20}{17} \\ = > x = \frac{180}{17} \\ = > x = 10.6 \: grams \: (approx.)\end{gathered}

x+y

x

×100

=>

x+60

x

×100=15

=>x=

100

15

×(x+60)

=>x=

20

3

(x+60)

=>x=

20

3

x+

20

3

×60

=>x−

20

3

x=3×3

=>

20

20−3

x=9

=>

20

17

x=9

=>x=9×

17

20

=>x=

17

180

=>x=10.6grams(approx.)