`NaCl` is added to`1` litre water to such an extent that `DeltaT_(f)//K_(f)` becomes to `(1)/(500)`,wt.of `NaCl` added to

Options

A. `5.85g`
B. `0.585`
C. `0.0585g`
D. None of these

Answer

C

Explanation

For`NaCl,i=2`
`:.(cancelOT_(f))/(K_(f))=2xxC_(m):.DeltaT_(f)=K_(f)xxixxC_(m)`
or,`(1)/(500)=2xx"molarity"`
or `"molality" =(1)/(1000)`
i.e.`(1)/(1000)` moles `Kg^(-1)`water
i.e,`(1)/(1000)` moles per litre water
`=(1)/(1000)xx58.5gNaCl`