When 20 $g$ of naphthoic acid is dissolved in 50 $g$ of benzene $(K_{f} = 1.72 K k g m o 1^{- 1})$ , a freezing point depression of 2 $K$ is observed. The van't Hoff factor (i) is:

0.5

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

1

No worries! We‘ve got your back. Try BYJU‘S free classes today!

2

No worries! We‘ve got your back. Try BYJU‘S free classes today!

3

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is B $0.5$
The expression for the depression in the freezing point is

$Δ T_{f} = K_{f} \times$ molality $\times i$ ......(i)

Here, $Δ T_{f}$ is the depression in the freezing point, $K_{f}$ is the freezing point depression constant, i is the van't Hoff factor and m is the molality of the solution.

The molality of a solution is the number of moles of naphthoic acid (solute) present in 1 kg of water (solvent).

The molar mass of naphthoic acid is $172 \times 10^{- 3} k g / m o l$

Hence, the molality of the solution is

$m = \frac{20}{172} \times \frac{1000}{50}$ m

Substitute values in equation (i)

$2 = 1.72 \times \frac{20}{172} \times \frac{1000}{50} \times i$

The van't Hoff factor is $i = 0.5$

Hence, the correct option is $A$

Suggest Corrections

Similar questions

When 20 g of naphthoic acid (C11H8O2) is dissolved in 50g of benzene (Kf = 1.72 K kg mol-1), a freezing point depression of 2K is observed. The van't Hoff factor (i) is -

Q. When

20 g

of naphthoic acid (

C_{1} 1 H_{8} O_{2}

) is dissolved in

50 g

of benzene

(K_{f}

1.72 K k g m o l^{- 1})

freezing point depression of

2 K

is observed. The van't Hoff factor

(i)

is:

Q. When 20 g of naphthoic acid

(C_{11} H_{8} O_{2})

is dissolved in 50 g of benzene

(K f = 1.72 k g m o l^{- 1})

, a freezing point depression of 2 K is observed. The Van’t Hoff factor (i) is

Q. When 20 g of naphthoic acid (

C_{11} H_{8} O_{2}

) is dissolved in 50 g of benzene (

K_{f} = 1.72 K K g m o l^{- 1}

), a freezing point depression of 2K is observed. The van’ t Hoff factor (i) is

QUESTION 2.33

19.5 g of $C H_{2} F C O O H$ is dissolved in 500g of water. The depression in the freezing point of water observed in 1.0 C. Calculate the van't Hoff factor and dissociation constant of fluoroacetic acid.
$K_{f} = 1.86 K k g m o l^{- 1}$

Join BYJU'S Learning Program

When 20 g of naphthoic acid is dissolved in 50g of benzene (Kf=1.72Kkgmo1−1), a freezing point depression of 2 K is observed. The van't Hoff factor (i) is:

When 20 $g$ of naphthoic acid is dissolved in 50 $g$ of benzene $(K_{f} = 1.72 K k g m o 1^{- 1})$ , a freezing point depression of 2 $K$ is observed. The van't Hoff factor (i) is: