Question

A solution containing 7.5 g of urea (molecular mass = 60) in 1 kg of water freezes at the same temperature as another solution containing 15 g of solute 'A' in the same amount of water. Calculate molar mass of 'A'.

• A. 120
• B. 20
• C. 110
• D. 60

Answer 1

The correct option is A 120

If the two solution have same freezing point then we have,

$m_1=m_2$

$\frac{7.5}{60\ast 1}=\frac{15}{x}$

therefore, molar mass of A (x) = 120 g