3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K. Calculate the van't Hoff factor and predict the nature of solute (associated or dissociated).

(Given: Molar mass of benzoic acid = 122 g mol^-1, K_ffor benzene = 4.9 K kg mol^-1

Solution

We know that the depression in freezing point is given by
$increment straight T subscript straight f space equals fraction numerator ik subscript straight f space straight x space straight w subscript straight s space straight x space 1000 over denominator straight M subscript straight s space straight x space straight W end fraction$

Here

Depression in freezing point K

K_f for benzene=4.9kg mol^-1

Mass of benzene W=49g

Molar mass of benzoic acid m_s= 122g mol^-1

Substituting the value we get

1.62 = $1.62 space equals fraction numerator straight i space straight x space 4.9 space straight x space 3.9 space straight x space 1000 over denominator 122 space straight x 49 end fraction i space equals space fraction numerator 1.62 space x space 122 space x space 49 over denominator 4.9 space x space 3.9 space x space 1000 end fraction space equals 0.51$
As the value of i<1 benzoic acid is associated solute.

Some More Questions From Solutions Chapter

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL at 37⁰C.

Suppose a solid solution is formed between two substances, one whose particles are very large and the other whose particles are very small. What kind of solid solution is this likely to be?

Amongst the following compunds identify which are insoluble, partially soluble and highly soluble in water?
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Solutions

3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K. Calculate the van't Hoff factor and predict the nature of solute (associated or dissociated).

(Given: Molar mass of benzoic acid = 122 g mol^-1, K_ffor benzene = 4.9 K kg mol^-1

Some More Questions From Solutions Chapter

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL at 37⁰C.

Suppose a solid solution is formed between two substances, one whose particles are very large and the other whose particles are very small. What kind of solid solution is this likely to be?

Amongst the following compunds identify which are insoluble, partially soluble and highly soluble in water?
(i) phenol (ii) toluene (iii) formic acid (iv) ethylene glycol (v) chloroform, (vi) pentanol.

Two liquids A and B boils at 145⁰C and 190⁰C respectively. Which of them has a higher vapour pressure at 80⁰C ?

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Solutions

3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K. Calculate the van't Hoff factor and predict the nature of solute (associated or dissociated). (Given: Molar mass of benzoic acid = 122 g mol-1, Kf for benzene = 4.9 K kg mol-1

Some More Questions From Solutions Chapter

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL at 370C.

Suppose a solid solution is formed between two substances, one whose particles are very large and the other whose particles are very small. What kind of solid solution is this likely to be?

Amongst the following compunds identify which are insoluble, partially soluble and highly soluble in water?(i) phenol (ii) toluene (iii) formic acid (iv) ethylene glycol (v) chloroform, (vi) pentanol.

Two liquids A and B boils at 1450C and 1900C respectively. Which of them has a higher vapour pressure at 800C ?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K. Calculate the van't Hoff factor and predict the nature of solute (associated or dissociated).

(Given: Molar mass of benzoic acid = 122 g mol^-1, K_ffor benzene = 4.9 K kg mol^-1

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL at 37⁰C.

Amongst the following compunds identify which are insoluble, partially soluble and highly soluble in water?
(i) phenol (ii) toluene (iii) formic acid (iv) ethylene glycol (v) chloroform, (vi) pentanol.

Two liquids A and B boils at 145⁰C and 190⁰C respectively. Which of them has a higher vapour pressure at 80⁰C ?