Question

16 g of a compound having molar mass 200 g/mol is mixed with 40 g of water and the solution formed has density 1.4 g/mL.
Find the correct option(s).

• A. The molality of the solution is $2{\text{mol kg}}^{-1}$
• B. The molarity of the solution is $2{\text{mol L}}^{-1}$
• C. The percentage by mass is $6.25\%$
• D. The percentage mass by vol is $40\%$

Answer 1

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

The correct options are
A The molality of the solution is $2{\text{mol kg}}^{-1}$
B The molarity of the solution is $2{\text{mol L}}^{-1}$
D The percentage mass by vol is $40\%$

$a)\text{Molality}=\frac{\frac{16}{200}\text{mol}}{\frac{40}{1000}\text{kg}}=2{\text{mol kg}}^{-1}$

$b)\text{Molarity}=\frac{\frac{16}{200}\text{mol}}{\frac{56}{1.4}\text{mL}}\times 1000=2{\text{mol L}}^{-1}$

$c)\text{Percent by mass}=\frac{16}{56}\times 100=28.6$

$d)\text{Percent mass by volume}=\frac{16}{\frac{56}{1.4}}\times 100=40$