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Phenol associates in benzene to certain extent to form a dimer. A solution containing `20 xx 10^(-3) kg` of phenol in `1.0 kg` of benzene hs its freezing point depressed by `0.69 K`. Calculate the fraction of phenol that has dimerized. (`K_(f)` for benzene is `5.12 K kg mol^(-1)`). |
Answer» Onserved mol. Mass `= (1000xxK_(f)xxw)/(WxxDeltaT)` `=(1000xx5.13xx20xx10^(-3))/(1xx0.69)=1.48.4` Normal mol. Mass of phenol `(C_(6)H_(5)OH)=94` So, `("Normal mol. mass")/("Observed mol. mass")=(94)/(148.4)` `=1+((1)/(n)-1)alpha=1+((1)/(2)-1)alpha` `(94)/(148.4)=1-(alpha)/(2)` or `alpha=0.733 or73.3%`. |
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