Question

In 90 g of 20% (w/w) aqueous salt solution 10 g more water is added. Calculate the final concentration (w/w%) of the solution.

Answer 1

Given:

The initial mass of solution = 90 gm

The initial mass percentage of aqueous salt solution = 20 %

The mass of water added = 10 gm

To Find:

The final concentration of the solution.

Calculation:

- The mass of salt in solution = 90 × 20 / 100 = 18 gm

- The final mass of solution = 90 + 10 = 100 gm

- The final mass percentage of the solution = (18 / 100) × 100

⇒ The final mass percentage of the solution = 18 %

- So, the final concentration of the solution is 18 % (w/w).

Answer 2

Given:

Solution's initial mass

= 90 g

Percentage

= 20%

Added water

= 10 g

To Find:

Final concentration = ?

Solution:

Mass of salt in solution will be:

=  $90\times \frac{20}{100}$

=  $18 \ g$

Final mass will be:

=  $90+10$

=  $100 \ g$

Now,

Final percentage of the solution will be:

=  $\frac{18}{100}\times 100$

=  $18 \ percent$

So that the final concentration will be "18%".