1. Tardigrade
  2. Question
  3. Chemistry
  4. A solution containing 0.1 g of a non-volatile organic substance P (molecular mass 100) in 100 g of benzene raises the boiling point of benzene by 0.2° C, while a solution containing 0.1 g of another non-volatile substance Q in the same amount of benzene raises the boiling point of benzene by 0.4° C. What is the ratio of molecular masses of P and Q ?

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Q. A solution containing $0.1 \,g$ of a non-volatile organic substance $P$ (molecular mass $100$) in $100 \,g$ of benzene raises the boiling point of benzene by $0.2^{\circ} C$, while a solution containing $0.1 \,g$ of another non-volatile substance $Q$ in the same amount of benzene raises the boiling point of benzene by $0.4^{\circ} C$. What is the ratio of molecular masses of $P$ and $Q$ ?

Solutions

Solution:

$\frac{(\Delta T)_{P}}{(\Delta T)_{Q}}=\frac{K_{b} \times\left(\frac{w_{B} \times 1000}{m_{B} \times w_{A}}\right)_{P}}{K_{b} \times\left(\frac{w_{B} \times 1000}{m_{B} \times w_{A}}\right)_{Q}}$
$\frac{0.2}{0.4}=\frac{\left(\frac{0.1 \times 1000}{100 \times 100}\right)_{P}}{\left(\frac{0.1 \times 1000}{100 \times w_{B}}\right)_{Q}}$
$\frac{1}{2}=\frac{\left(m_{B}\right)_{Q}}{100} m_{B}=50$
$\therefore \left(m_{B}\right)_{P}:\left(m_{B}\right)_{Q}$
$=100: 50=2: 1$