Question

300 gm of 25% w/w solution of solute A is mixed with 400 gm of 40 (w/w) solution of another solute B. What is the w/w percentage of the new mixture?
(A) 10.71% in A
(B) 35% in B
(C) 25% in A
(D) 40 % in B

Answer 1

Hint: w/w % of a solute in a solution can be calculated by dividing the % of solute multiplied with the mass of that solute in the solution, by the total mass of all solutes in the solution. Using this formula we can solve the following numerical.

Complete step by step solution:

Solute A of 300gm of 25% w/w is mixed with solute B of 400gm of 40% w/w to form a solution. Therefore, w/w % of solute A can be calculated as:
w/w % of solute A $\text{=}\dfrac{\text{25 }\\!\\!\%\\!\\!\text{ of 300}}{\text{300+400}}\text{=}\dfrac{\text{75}}{\text{700}}\text{ }\\!\\!\times\\!\\!\text{ 100=10}\text{.71 }\\!\\!\%\\!\\!\text{ }$
Similarly, the w/w % of solute B can be calculated as:
w/w % of B $\text{=}\dfrac{\text{40 }\\!\\!\%\\!\\!\text{ of 400}}{\text{300+400}}\text{ }\\!\\!\times\\!\\!\text{ 100=22}\text{.85 }\\!\\!\%\\!\\!\text{ }$
Therefore, the correct answer from the given is 10.71% in A, because w/w % of solute A is 10.71%.
Hence, the correct option is Option A.

Additional Information: There are three types of solutions that can occur based on the solute concentration isotonic, hypotonic and hypertonic.
Isotonic solutions contain equal concentrations of impermeable solute on either side of the membrane and so the cell does not shrink.

A solution that contains fewer dissolved particles and is found in normal cells and blood is called hypotonic solution.
Hypertonic solution is a particular type of solution that has a greater concentration of solutes on the outside of a cell when compared with the inside of a cell.

Note: We should know that the concentration of a solution indicates the relative amount of solute and solvent which is present. Knowing the concentration of the solution, is very important to predict the consequences of the chemical equations.