The depression in freezing point is `0.24` K obtained by dissolving `1g NaCl` in 200 g water. Calculate van't-Hoff factor. The molar depression constant is `1.86 K kg mol ^(-1).`

Explanation

Molar mass of solute `= (1000 xx K _(f) xx "Mass of NaCl")/(Delta T_(f) xx "Mass of solvent")`
` =(1000 xx 1. 86 xx 1)/(0.24 xx 200) = 38.76g mol ^(-1)`
Theoretical molar mass of NaCl is `= 38.75 g mol ^(-1)`
`i=("Theoretic molar mass")/("Experimental molar mass") = (58.5)/(38.75) = 1. 50`