Question

The molality of the solution containing 15.20 g of urea (molar mass = 60) dissolved in 150 g of water is:

• A. $1.689molk{g}^{-1}$
• B. $0.1689molk{g}^{-1}$
• C. $0.5922molk{g}^{-1}$
• D. $0.2533molk{g}^{-1}$

Answer 1

Answer: (A)

$1.689molk{g}^{-1}$

$\text{molality}=\frac{\text{mass of urea}}{\text{molar mass of urea}\times \text{mass of water in kg}}$

$\text{molality}=\frac{\text{15.20 g}}{\text{60 g/mol}\times \text{0.150 kg}}$

$\text{molality}=\text{1.689 mol/kg}$

Hence, option A is correct.