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  • Need clarity, kindly explain! - Molecules of benzoic acid dimerise in benzene. 'w' g of the acid dissolved in 30 g of benzene shows - Some basic concepts in chemistry - JEE Main

Molecules of benzoic acid (C_{6}H_{5}COOH) dimerise in benzene. 'w' g of the acid dissolved in 30 g of benzene shows a depression in freezing point equal to 2 K. If the percentage association of the acid to form dimer in the solution is 80, then w is :

(Given that Kf = 5 K kg mol -1, Molar mass of benzoic acid = 122 g mol-1)

  • Option 1)

    2.4 g

  • Option 2)

    1.5 g

  • Option 3)

    1.8 g

     

  • Option 4)

    1.0 g 

Answers (1)

best_answer

 

Mole Concept -

One mole is the amount of a substance that contains as many particles or entities as there are atoms in exactly 12 g (or 0.012 kg) of the 12C isotope.

- wherein

one mole = 6.0221367 X 1023   

Molar Mass -

The mass of one mole of a substance in grams is called its molar mass.

- wherein

 Molar mass of water = 18 g mol-1

As e have learned:

The reaction is :

2\left ( C_{6}H_{5}-COOH \right )\xrightarrow[30g]{C_{6}H_{6}}\left ( C_{6}H_{5}COOH \right )_{2}

\Delta _{f}T=iK_{f}m

2=0.6\times 5\times \frac{w\times 1000}{122\times 30}

(i=1-0.8+0.4=0.6)

w=2.44g


Option 1)

2.4 g

Option 2)

1.5 g

Option 3)

1.8 g

 

Option 4)

1.0 g 

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