Question

A solution is prepared by adding 2g of a substance A to 18g of water. Calculate the mass percent of the solute.

Answer 1

Hint: The mass percentage of solute is defined as a way of expressing the concentration of the solute when mass of solute and solvent is given. The mass percentage of solute is calculated by dividing the mass of solute with the total mass of the solution multiplied by 100.

Complete step by step answer:
Given,
The mass of substance A is 2g.
The mass of water is 18 g.
Here, the substance is the solute and water is the solvent. The substance is dissolved in water to form the solution.
In the given question, it is said that we need to find out the mass percent of the solute. The mass percent of the solute is defined as the mass of solute divided by the mass of solute plus mass of the solvent (mass of solution) multiplied by 100.
The formula for calculating the mass percent is shown below.
$M\% = \dfrac{{{M_s}}}{{{M_T}}} \times 100$
Where,
M% is the mass percent of solute.
${M_S}$ is mass of solute
${M_T}$ is the mass of solute and solvent (Total mass of solution)
To find out the mass % of the solute, substitute the given values in the above equation.
$\Rightarrow M\% = \dfrac{{2g}}{{2g + 18g}} \times 100$
$\Rightarrow M\% = \dfrac{{2g}}{{20g}} \times 100$
$\Rightarrow M\% = 0.1g \times 100$
$\Rightarrow M\% = 10\%$

Therefore, the mass percentage or M% of the solute is 10%.

Note: There is another method to calculate the concentration of the solute if the values are given in terms of milliliter. The concentration of the solute is calculated by volume percentage. In this formula, the volume of solute is divided by the total volume multiplied by 100.