Question

A solution containing 1.8 g of a compound (empirical formula `CH_(2)O`) in 40 g of water is observed to freeze at `-0.465^(@)`C. The molecules formulea of the compound is (`K_(f)` of water =1.86kg K`mol^(-1)`):
A. `C_(2)H_(4)O_(2)`
B. `C_(3)H_(6)`
C. `C_(4)H_(8)O_(4)`
D. `C_(6)H_(12)O_(6)`

Answer 1

`M_(2) = (1000k_(f)w_(2))/(w_(1) xx DeltaT_(f)) =(1000 xx 1.86 xx 18)/(40 xx 0.0465) = 180`
EM mass `CH_(2)O = 30`
`:. n = (180)/(30) = 6`
`:.` molecular formula `= 6 xx CH_(2)O = C_(6)H_(12)O_(6)`