The addition of 3 g of a substance to 100 g CCl 4 M = 154 g mol - 1 raises the boiling point of CCl 4 by 0 . 60 ° C . If K b CCl 4 is 5 K mol - 1 kg , calculate the freezing point depression. Given : K f CCl 4 = 32 . 0 K kg mol - 1 .

Given: weight of solute = 3 g , ∆ T b = 5 . 03 K Kg mole - 1 , K f = 32 . 0 K Kg mole - 1 The depression in freezing point ∆ T f = K f × m The elevation in boiling point ∆ T b = K b × m where K f = molal depression constant K b = molal elevation constant m = molality thus, ΔT f ΔT b = K f K b ⇒ ΔT f = 32 5 . 03 × 0 . 6 ⇒ ∆ T f = 3 . 793 ˚ C Hence, the freezing point depression is 3 . 793 ˚ C

A solution containing 0 . 011 kg of barium nitrate Ba NO 3 2 in 0 . 1 kg of water boils at 100 . 46 ° C . Calculate the degree of ionization of the salt. K b (water) = 0 . 52 K kg mol - 1 . Ba = 137

Given: Weight of barium nitrate = 0 . 011 kg , the boiling point of water = 100 . 46 ° C , K b = = 0 . 52 K kg mol - 1 Elevation in boiling point = 100 . 46 ° C - 100 ° C = 0 . 46 ° C But ∆ T b = iK b m Where m = molality m = moles of solute wt . of solvent Kg m = 0 . 011 × 10 3 261 0 . 1 ⇒ 0 . 46 = i × 0 . 52 × 0 . 011 × 10 3 0 . 1 × 261 ⇒ i = 2 . 098 Degree of ionization α = i - 1 n - 1 n = 3 for Ba NO 3 2 ⇒ α = 2 . 098 - 1 3 - 1 ⇒ α = 0 . 55 Hence, the degree of ionization of the salt is 0 . 55

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Beta Question Bank for Engineering: Chemistry>Chapter 8 - Solutions>EXERCISE-2>Q 42

Which of the following plots represents an ideal binary mixture?

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Beta Question Bank for Engineering: Chemistry>Chapter 8 - Solutions>EXERCISE-2>Q 43

Acetone and carbon disulphide form binary liquid solution showing positive deviation from Raoult law. The normal boiling point

(T_{b})

of pure acetone is less than that of pure

{CS}_{2}

. Pick out the incorrect statements among the following.

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Beta Question Bank for Engineering: Chemistry>Chapter 8 - Solutions>EXERCISE-3>Q 16

The freezing point of ether was lowered by

0.60 ° C

on dissolving

2.0 g

of phenol in

100 g

of ether. Calculate the molar mass of phenol and comment on the result. Given :

K_{f}

(ether)

= 5.12 K kg {mol}^{- 1}

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Beta Question Bank for Engineering: Chemistry>Chapter 8 - Solutions>EXERCISE-3>Q 17

The addition of

3 g

of a substance to

100 g {CCl}_{4} (M = 154 g {mol}^{- 1})

raises the boiling point of

{CCl}_{4}

0.60 ° C

. If

K_{b} ({CCl}_{4})

5 K {mol}^{- 1} kg

, calculate the freezing point depression.
Given :

K_{f} ({CCl}_{4}) = 32.0 K kg {mol}^{- 1}

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Beta Question Bank for Engineering: Chemistry>Chapter 8 - Solutions>EXERCISE-3>Q 18

500 gm

of water

3.0 \times 10^{- 3} kg

of acetic acid is added. If

23 %

of acetic acid is dissociated, what will be the depression of freezing point?

K_{f} = 1.86 K kg {mol}^{- 1}

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Beta Question Bank for Engineering: Chemistry>Chapter 8 - Solutions>EXERCISE-3>Q 19

0.01 m

aqueous solution of

K_{3} [Fe {(CN)}_{6}]

freezes at

- 0.062 ° C .

What is the apparent percentage of dissociation ? (

K_{f}

for water

= 1.86 K kg {mol}^{- 1}

)

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Beta Question Bank for Engineering: Chemistry>Chapter 8 - Solutions>EXERCISE-3>Q 20

A solution containing

0.011 kg

of barium nitrate

[Ba {({NO}_{3})}_{2}]

0.1 kg

of water boils at

100.46 ° C

. Calculate the degree of ionization of the salt.

K_{b}

(water)

= 0.52 K kg {mol}^{- 1}

[Ba = 137]

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Beta Question Bank for Engineering: Chemistry>Chapter 8 - Solutions>EXERCISE-3>Q 24

A certain mass of a substance, when dissolved in

100 g C_{6} H_{6}

, lowers the freezing point by

1.28 ° C

. The same mass of solute dissolved in

100 g

water lowers the freezing point by

1.40 ° C

. If the substance has normal molecular weight in benzene and is completely ionized in water, into how many ions does it dissociate in water?

K_{f}

for

H_{2} O

and

C_{6} H_{6}

are

1.86

and

5.12 K kg {mol}^{- 1}

The relative lowering of the vapour pressure is equal to the ratio between the number of

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