Home
Class 12
CHEMISTRY
In an experiment, 72.5 g of C(6)H(5)OH (...

In an experiment, `72.5 g` of `C_(6)H_(5)OH` (phenol) is dissolved in a solvent of `K_(f)=14`. If the depression in freezing point is `7 K`, find the percentage of phenol that dimerizes.

Text Solution

Verified by Experts

The correct Answer is:
`alpha=70%`
Phenol is dimerized as follows:
`2C_6H_5OHhArr(C_6H_5OH)_2`
`{:(At t=0,1,0),(At Eq,(1-alpha),alpha//2):}`
Total moles after dimerization
=`1-alpha+alpha//2=1-alpha//2`
Van't Hoff factor
=`"Normal molecular weight of phenol"/"Abnormal molecular weight of phenol"=94/Mw_(ab)`
`Mw_(ab)=(1000xxK_(f)xxW_(2))/(DeltaT_(f)xxW_(1))`
Given that, `K_(f)=14`
`W_(2)=72.5 g`
`W_(1)=1000 g`
`:. Mw_(ab)=(1000xx14xx72.)/(7xx1000)=145`
`:. i=94/145`
(i)=`" Number of particles after dimerizaion"/"Number of particles before dimerizaion"`
`=(1-alpha//2)/1`
From Eqs.(i) and (ii), we get
`1-alpha//2=94/145=0.65`
`alpha/2=1-0.65=0.35 :. alpha=70%`
Hence, `70%` phenol is present in dimeric form.
Promotional Banner

Similar Questions

Explore conceptually related problems

1575.2 g of C_(6)H_(5)OH (phenol) is dissolved in 960 g of a solvent of solvent of K_(f)=14 K kg mol^(-1) . If the depression in freezing point is 7 K , then find the percentage of phenol that dimerizes.

When 20 g of naphthoic acid (C_(11)H_(8)O_(2)) is dissolved in 50 g of benzene ( K_(f)=1.72 "K kg mol"^(-1) ) a freezing point depression of 2K is observed. The Van't Hoff factor (i) is :

When 20 g of naphthoic acid (C_(11)H_(8)O_(2)) is dissolved in 50 g of benzene (K_(f)=1.72 K kg mol^(-1)) , a freezing point depression of 2 K is observed. The Van't Hoff factor (i) is

When dissolved in benzene, a compound C_(38)H_(30) partilly dissociates by the following equation: 25.6 g of C_(38)H_(30) is dissolved in 400 g of benzene, the freezing point is lowered by 0.680^(@)C . What percentage of C_(38)H_(30) molecules have dissociated? (K_(f)=4.9)

Two grams of benzoic acid (C_(6)H_(5)COOH) dissolved in 25.0 g of benzene shows a depression in freezing point equal to 1.62 K . Molal depression constant for benzene is 4.9 K kg^(-1)"mol^-1 . What is the percentage association of acid if it forms dimer in solution?

Phenol associates in benzene to a certain extent to form a dimer. A solution containing 20 g of phenol in 1.0 kg of benzene has its freezing point lowered by 0.69 K. Calculate the fraction of phenol that has dimerised. [Given : K_(f) for benzene = 5.1 Km^(-1)]

1.355 g of a substance dissolved in 55 g of CH_(3)COOH produced a depression in the freezing point of 0.618^(@)C . Calculate the molecular weight of the substance (K_(f)=3.85)

If the elevation in boiling point of a solution of non-volatile, non-electrolytic and non-associating solute in a solvent ( K_(b)=x "K kg mol"^(-1) ) is y K, then the depression in freezing point of the same concentration would be ( K_(f) of the solvent = z "K kg mol"^(-1) )

0.6 mL of acetic acid (CH_(3)COOH) having density 1.06 g mL^(-1) is dissolved in 1 L of water. The depression in freezing point observed for this strength of acid was 0.0205^(@)C .Calculate the Van't Hoff factor and dissociation constant of the acid. K_(f) for H_(2)O=1.86 K kg ^(-1) "mol"^(-1))

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) ).