A non -volatile solute.'A' tetramerises in water to the extent of 80% .2.5 g of 'A' in 100 g of water .lower the freezing point by 0.3 `""^(@)C`.The molar mass of Å in mol `4^(-1)` is (`K_(T)`For water =1.86 K kg `mol^(-1)`)

Options

A. 221
B. 62
C. 354
D. 155

Answer

B

Explanation

`DeltaT_(r)=iK_(r)xxm`
`0.3=(ixx1.86xxomega_(2)xx1000)/(M_(2)xxomega_(1))`
`0.3=(0.4xx1.86xx2.5xx1000)/(M_(2)xx100)impliesM_(2)=62`