Pure benzene freeze at ${5.45}^{\circ} C . A$ solution containing 7.24 g of $C_{2} H_{2} C l_{4}$ in 115.3 g of benzene was observed to freeze at ${3.55}^{\circ} C$ . What is the molal freezing point constant of benzene?

{20.8}^{\circ} C / m

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

{10.4}^{\circ} C / m

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

{2.04}^{\circ} C / m

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

{5.08}^{\circ} C / m

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

Open in App

Solution

The correct option is D ${5.08}^{\circ} C / m$
Depression in the freezing point $= Δ T_{f} = 5.45 - 3.55 = {1.9}^{o} C$
Molar mass of $C_{2} H_{2} C l_{4} = 12 \times 2 + 2 \times 1 + 4 \times (35.5) = 168$ g/mol
The number of moles is the ratio of mass to molecular weight.
Number of moles of solute $= \frac{7.24}{168} = 0.0431$
The molality of solution is the number of moles of solute in $1000$ g of water.
Molality $= \frac{0.0431 \times 1000}{115.3} = 0.374$
Depression in the freezing point :

$Δ T_{f} = K_{b} m ⟹ 1.9 = K b \times 0.374$

$K_{b} = 5.08^{o} C / m$

Suggest Corrections

Similar questions

Q. Pure benzene freezes at

{5.45}^{\circ} C

. A

0.374 m

solution of tetrachloroethane in benzene freezes at

{3.55}^{\circ} C

K_{f}

for benzene is:

Pure benzene freezes at 5.45°C at a certain places but a 0.374 m solution of tetrachloroethane In benzene freezes at 3.55°C. The $K_{f}$ for benzene is

Q. When a

0.374 m

of tetrachloroethane is added to benzene, the solution freezes at

{3.55}^{\circ} C

. Find the

K_{f}

of benzene?
[Pure benzene freezes at

{5.45}^{o} C

]

Pure benzene freezes at 5.45°C at a certain places but a 0.374 m solution of tetrachloroethane In benzene freezes at 3.55°C. The $K_{f}$ for benzene is

Q. Pure benzene freezes at

{5.45}^{o} C

at a certain but a

0.374

m solution of tetrachloroethane in thane benzene freezes at

{3.55}^{o} C

. The

K_{f}

for benzene is ?

Join BYJU'S Learning Program

Pure benzene freeze at 5.45∘C.A solution containing 7.24 g of C2H2Cl4 in 115.3 g of benzene was observed to freeze at 3.55∘C. What is the molal freezing point constant of benzene?

Pure benzene freeze at ${5.45}^{\circ} C . A$ solution containing 7.24 g of $C_{2} H_{2} C l_{4}$ in 115.3 g of benzene was observed to freeze at ${3.55}^{\circ} C$ . What is the molal freezing point constant of benzene?