A solution is prepared by adding 2 g of "X" to 1 mole of water. Mass percent of "X" in the solution is.

Given: Mass of solute X = 2 g and moles of solvent H2 O = 1 mole. Find: Mass percent of X in the solution. The molar mass of water is 18 g/mol So, mass of solvent is 1 mol 18 g/mol = 18 g Total mass of solution is 2 g + 18 g = 20 g Mass percent of X is mass of X = Mass of X Total mass 100 = 220 100 = 10 Therefore, the mass percent of X in the solution is 10. The solution working gives this result, so the correct option is D. The solution shows option C, which disagrees with the actual calculation.

A solution is prepared by adding 2 g of "X" to 1 mole of water. M… — Solution | JEE Chemistry

MCQEasyJEE 2023Concentration Terms (Molarity, Molality, etc.)

A solution is prepared by adding $2 \, \text{g}$ of "X" to $1$ mole of water. Mass percent of "X" in the solution is _____.

A
$5\%$
B
$20\%$
C
$2\%$
D
$10\%$

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: Mass of solute $X = 2 \, \text{g}$ and moles of solvent $\text{H}_2\text{O} = 1$ mole.

Find: Mass percent of $X$ in the solution.

The molar mass of water is

18 \, \text{g/mol}

So, mass of solvent is

1 \, \text{mol} \times 18 \, \text{g/mol} = 18 \, \text{g}

Total mass of solution is

2 \, \text{g} + 18 \, \text{g} = 20 \, \text{g}

Mass percent of $X$ is

\%\text{ mass of } X = \frac{\text{Mass of } X}{\text{Total mass}} \times 100 = \frac{2}{20} \times 100 = 10\%

Therefore, the mass percent of $X$ in the solution is $10\%$ . The solution working gives this result, so the correct option is D. The solution shows option C, which disagrees with the actual calculation.

Common mistakes

Using $1$ mole of water as if its mass were $1 \, \text{g}$ is incorrect because mole and gram are different quantities. First convert moles of water to mass using its molar mass $18 \, \text{g/mol}$ .
Dividing by only the mass of solvent is incorrect because mass percent is based on total mass of solution. Add solute and solvent masses first to get $20 \, \text{g}$ .
Choosing the option from the solution without checking the calculation is incorrect here because the header label conflicts with the worked steps. Follow the numerical working and then map to the matching option.

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Answer

Step-by-step solution

Common mistakes

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