Question

A solution is obtained by mixing 200g of 30% and 300g of 20% solution by weight. What is the percentage of solute in the final solution?
(A) 50%
(B) 28%
(C) 64%
(D) 24%

Answer 1

Hint: mass of solute in 200g of 30% is 60g and mass of solute in 300g of 20% solution is also 60g. Total mass of solute is 120 g and total mass of solution is 500g. percentage of solute can be calculated by dividing mass of solute to mass of solution, ratio obtained multiplied by 100.

Complete solution step by step:
Mass of solute is obtained by multiplying % weight with mass of solvent and obtaining an answer divided by 100.
Mass of solute in 200g of 30% solution can be obtained as follows:
30% by weight indicates 30g of solute is present in 100g of solvent so 60g of solute will be present in 200g of solution.
20% by weight indicates 20g of solute is present in 100g of solvent so 60g of solute will be present in 300g of solution
So on mixing these both solutions, mass of solute is 60g +60g =120g
Mass of solution on mixing is 200g +300g =500g
Percent of solute can be obtained as follows:
\[\text{percent of solute=}\dfrac{\text{mass of solute}}{\text{mass of solution}}\times 100\]
= $\dfrac{120}{500}\times 100$= 24%

24% percentage of solute in the final solution.

Note: % Weight indicates mass of solute present in 100g of solution. The solution is composed of solute and solvent. Mass of solute is obtained by multiplying % weight with mass of solvent and obtaining an answer divided by 100. Mass percent of solute=(mass of solute/ mass of solution) x 100.