1.

A solution containing 1.8 g of a compound (empirical formula CH_(2)O) in 40 g os water is observed to freeze at -0.465^(@)C. The molecular formula of the compound is (K_(f) "of water" =1.86 kg K mol^(-1))

Answer»

`C_(2)H_(4)O_(2)`
`C_(3)H_(6)O_(3)`
`C_(4)H_(8)O_(4)`
`C_(6)H_(12)O_(6)`

SOLUTION :`Delta T_(f)=K_(f)xxm`
`0.465=1.86xx(1.8)/(M)xx(1000)/(40)rArr M =180`
MOLECULAR formula = `("EMPIRICAL formula")_(n)`
`n=("Molecular mass")/("Empirical formula mass")=(180)/(30)=6`
Molecular formaula `= (CH_(2)O)_(6)=C_(6)H_(12)O_(6)`.


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