Question

50 gm of a compound (molar mass 200 gm/mol and density 0.6 gm/ml) is mixed in 200 gm of a solvent (density 1.2 kg/L)
List-I contains concentration terms for the solutions formed and List-II contains the concentration.
$\begin{array}{cccc}& \text{List-I}& & \text{List-II}\\ \left(I\right)& \text{Molarity (mol/L)}& \left(P\right)& 20\\ \left(II\right)& \text{Molality (mol/kg)}& \left(Q\right)& 0.67\\ \left(III\right)& \%\text{mass by mass}& \left(R\right)& 1.2\\ \left(IV\right)& \%\text{mass by volume (g/ml)}& \left(S\right)& 1\\ & & \left(T\right)& 25\\ & & \left(U\right)& 1.25\end{array}$

Which of the following options has the correct combination considering List-I and List-II

• A. (II),(S) and (III),(T)
• B. (II),(U) and (III),(T)
• C. (II),(R) and (II),(P)
• D. (II),(U) and (III),(P)

Answer 1

The correct option is D (II),(U) and (III),(P)

(II) Molality,
$m=\frac{\frac{50}{200}}{\frac{200}{1000}}=\frac{5}{4}=1.25mol/kg$.
(III) Mass of the solution $=50g+200g=250g$
$\%bymassofthesolution=\left(\frac{50}{250}\right)\times 100=20$