Home
Class 12
CHEMISTRY
12.2 g of benzonic acid (molar mass = 12...

12.2 g of benzonic acid (molar mass = 122 ) in 100 g of benzene has a depression in freezing point `2.6^(@)`. If there is 100 percent polymersation, what is the nunber of molecues of benzoic acid in associated state ? (Given `K_(f)` for benzene =5.2 K kh `mol^(-1)`)

Text Solution

Verified by Experts

The correct Answer is:
Dimar
Observed molar mass of benzoic acid may be calculated as follows :
`M_(B)=(K_(f)xxW_(B))/(DeltaT_(f)xxW_(A))`
`W_(B)=12.2g, W_(A)=100g=0.1 kg, K_(f)=5.2" K kg mol"^(-1), DeltaT_(f)=2.6 K`
`M_(B)=((5.2" K kg mol"^(-1))xx(12.2 g))/((2.6 K)xx(0.1"kg"))=244.0" g mol"^(-1)`
`"On comparison, observed molar mass "(244" g mol"^(-1)) "of benzoic acid is twice its normal molar mass (122" g mol"^(-1))`.
This means that benzoic acid exists as a dimer in the associated state.
Promotional Banner

Similar Questions

Explore conceptually related problems

12.2 g of benzoic acid (Mw=122) in 100 g benzene has depression in freezing point 2.6^(@) , K_(f)=5.2^(@) kg mol^(-1) . If there is 100% polymerzation, the number of molecules of benzoic acid in associated state is

12.2 g of benzoic acid (Mw=122) in 100 g water has elevation in boiling point of 0.27.K_(b)=0.54 K kg mol^(-1) .If there is 100% polymerization, the number of molecules of benzoic acid in associated state is

12.2g of benzoic acid in 100 g water decreases freezing point upto -0.93^@C K_f = 1.86KKG/mole. if there is 100% polymerisation, the number of molecules of benzoic acid in associated state is

12.2gm benzoic acid (M =122) in 100g H_(2)O has elevation of boiling point of 0.27^(@)C, K_(b) = 0.54 K kg/mole. If there is 100% dimerization the no.of molecules of benzoic acid in associated sate is:

Molecules of benzoic acid (C_(6)H_(5)COOH) dimerise in benzene. ‘w’ g of the acid dissolved in 30g of benzene shows a depression in freezing point equal to 2K. If the percentage association of the acid to form dimer in the solution is 80, then w is : (Given that K_(f)=5K Kg "mol"^(-1) Molar mass of benzoic acid =122 g "mol"^(-1) )

2.44 g 'w' g of the benzoic acid dissolved in 30 g of benzene shows depression in freezing equal to 2K. If the percentage association of the acid to form polymer (C_(6)H_(5)COOH)_(n) in the solution is 80, then find numerical value of n. (Given that K_(f) = 5K kg mol^(-1) , Molar mass of benzoic acid = 122 g mol^(-1) )