If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution , the change in freezing point of water `(DeltaT_(f))` when `0.01` mole of sodium sulphate is dissociated in 1 kg of water is : (`K_(f) = 1.86` K kg `mol^(-1)`)

Options

A. 0.0744 K
B. 0.0186 K
C. 0.0372 K
D. 0.0558 K

Answer

D

Explanation

For complete dissoication of `Na_(2)SO_(4)`
`Na_(2)SO_(4) to 2Na^(+) + SO_(4)^(2-)`
` i= 3`
`m =(0.01)/(1) xx 1 = 0.01`
`Delta T_(f) = iK_(f) m`
` = 3 xx 1.86 xx 0.01`
`Delta T_(f) = 0.0558K`