Question

20 g of a compound that has a molar mass 250 g/mol is added to 20 g water, and the solution formed has a density of 1.5 g/ml. Find correct option(s) among the following:

• A. The molality of the solution is $4$ mol/kg
• B. The molarity of the solution is $3$ mol/L
• C. The percentage by mass is $50$
• D. The percentage mass by vol is $75$

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A The molality of the solution is $4$ mol/kg
B The molarity of the solution is $3$ mol/L
C The percentage by mass is $50$
D The percentage mass by vol is $75$

$a)Molality=\frac{\frac{20}{250}mol}{\frac{20}{1000}kg}=4molk{g}^{-1}$
$b)Molarity=\frac{\frac{20}{250}mol}{\frac{40}{1.5}ml}\times 1000=3mol{L}^{-1}$
$c)Percentbymass=\frac{20}{40}\times 100=50$
$d)Percentmassbyvolume=\frac{20}{\frac{40}{1.5}}\times 100=75$