Question

400g solution having 20%(w/w) solute is cooled then 50g solute precipitated. What is the %(w/w) of solute in remaining solution?

Answer 1

Answer : The %(w/w) of solute in remaining solution is, 8.57%

Explanation :

First we have to calculate the mass of solute.

$Mass\%=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 100$

$20\%=\frac{\text{Mass of solute}}{400g}\times 100$

$\text{Mass of solute}=80g$

Now we have to calculate the mass of remaining solution.

The mass of remaining solution = Total mass of solution - Mass of precipitated solute

The mass of remaining solution = 400 - 50 = 350 g

The mass of remaining solute = 80 - 50 = 30 g

Now we have to calculate the %(w/w) of solute in remaining solution.

$\%(w/w)\text{ of solute}=\frac{\text{Mass of solute}}{\text{Mass of remaining solution}}\times 100$

$\%(w/w)\text{ of solute}=\frac{30g}{350g}\times 100=8.57\%$

Therefore, the %(w/w) of solute in remaining solution is, 8.57%

Answer 2

Answer : The %(w/w) of solute in remaining solution is, 8.57%

Explanation :

First we have to calculate the mass of solute.

Mass\%=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 100Mass%=

Mass of solution

Mass of solute

×100

20\%=\frac{\text{Mass of solute}}{400g}\times 10020%=

400g

Mass of solute

×100

\text{Mass of solute}=80gMass of solute=80g

Now we have to calculate the mass of remaining solution.

The mass of remaining solution = Total mass of solution - Mass of precipitated solute

The mass of remaining solution = 400 - 50 = 350 g

The mass of remaining solute = 80 - 50 = 30 g

Now we have to calculate the %(w/w) of solute in remaining solution.

\%(w/w)\text{ of solute}=\frac{\text{Mass of solute}}{\text{Mass of remaining solution}}\times 100%(w/w) of solute=

Mass of remaining solution

Mass of solute

×100

\%(w/w)\text{ of solute}=\frac{30g}{350g}\times 100=8.57\%%(w/w) of solute=

350g

30g

×100=8.57%

Therefore, the %(w/w) of solute in remaining solution is, 8.57%