The freezing point of water is depressed by ` 0.37^@C` in a 0.01 molal NaCI solution. The freezing point of 0.02 molal solution of urea is depressed by

Options

A. `0.37^(@)C`
B. `0.74^(@)C`
C. `0.185^(@)C`
D. `0^(@)C`

Answer

A

Explanation

The depression in freezing point is proportional to molal concentration of the solute i.e.
`Delta T_(f) prop m`
`Delta T_(f)=K_(f)mi` or `K_(f)=(Delta T_(f))/(ixxm)` = constant
so, `(Delta T_(f_(NaCl)))/(i_(NaCl)xxm_(NaCl))=(Delta T_(f_("Urea")))/(m_("Urea")xxi_("Urea"))` = constant
`(0.37)/(2xx0.01)=(Delta T_(f_("Urea")))/(0.02xx1)rArr Delta T_(f_("Urea"))=(0.37xx0.02)/(0.02)=0.37^(@)C`.