Question

A salt solution is prepared by dissolving 60g of salt in 140g of water. Calculate the amount of solute that should be added to make it's concentration 50% (w/w).

Answer 1

Answer:

the amount of solute that should be added is 30%

Answer 2

Answer:

40g

Explanation:

The initial mass of the salt = 60 g

The initial mass of water = 140 g

We know that,

Mass of solution = solute + solvent = 60 + 140

Mass of solution = 200 g

$\text {Percentage concentration by mass }= \dfrac {solute}{solution} \times 100= \dfrac {60}{200}\times 100 \\\\\text {Percentage concentration by mass }= 30\%$

By using the unitary method we can write

If concentration by mass is 30%, then solute = 60 g

When % concentration by mass is 50%,  then solute will also double that is 100%

Therefore 100g of salt should be present in the solution to make its concentration by 50%.

So we need, 100 – 60 = 40g more amount of salt to be added in the solution.