Question

When 200 g of 10 % (weight of solute/weight of solvent) solution was cooled, part of the solute precipitated and the concentration of solution become 6 % (weight of solute/weight of solvent). The mass of the precipitated solute is

Answer 1

Hint: As we know that the solution is mainly composed of solute and solvent. The mass percent of solute is given by the formula that is mass of solute divided by the mass of solution, then whole multiplied by 100.

Complete step by step answer:
In the lower classes, we have studied the calculations of basic entities like mass percent, the molecular weight of the chemicals, and many others. Let us see in detail the calculation of mass percent of the given solute.
- As we are being provided with the value of the weight of the solution which is equal to 200 g. The question says that the weight of the solute is equal to 10 % of 200. This means is equal to 20 g.
- We have to find the weight percentage of solute precipitate (x). Therefore, we can write the solute remained will be 20 - x.
- The concentration of the remaining solution becomes 6 %. We can write the weight of solution remained is = 200 - x
- We will find the Mass percent of solute which is given by the formula that is mass of solute divided by the mass of solution, then whole multiplied by 100.
Mass percent = $\dfrac{{{m}_{solute}}}{{{m}_{solution}}}\times 100$
By substituting the values we have,
6% = $\dfrac{20-x}{200-x}\times 100$
\[\Rightarrow 2000-100x = 1200-6x\]
Thus, by simplifying the above equation, the value of x will be,
\[94x=800\]
\[\Rightarrow x=8.51g\]
 - Hence, we can conclude that the mass of the precipitated solute is 8.51 gm.

Note: - As we know that the percentage weight indicates the mass of solute that is present in solution or we can say describes the component in a particular mixture. It is found that the amount of solute is basically expressed in mass or by moles.