1.4 g of acetone dissolved in 100 g of benzene gave a solution which freezes at 277.12 K. Pure benzene freezes at 278.4 K. 2.8g of solid (A) dissolved in 100 g of benzene gave a solution which froze at 277.76 K. Calculate the molecular mass of (A).

562

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

462

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

362

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

232

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

Open in App

Solution

The correct option is D 232
Here compare both the cases and get the answer.
How?
Let’s find out.
We know that
$Δ T = K_{f} \times \frac{W_{2} \times 1000}{M w_{2} \times w_{1}}$
Where $Δ T$ = Depression in freezing point
$K_{f}$ = Molal depression constant of benzene
$W_{2}$ = Mass of solute
$M w_{2}$ = Molecular mass of solute
$W_{1}$ = Mass of solvent
Case I: $(278.4 - 277.12) = K_{f} \times \frac{1.4 \times 1000}{50 \times 100}$
$1.28 K_{f} \times \frac{14}{58} . . . . . (i)$
Case II: $(278.4 - 277.76) = K_{f} \times \frac{2.8 \times 1000}{M w_{A} \times 100}$
$0.64 = K_{f} \times \frac{28}{M w_{A}}$
Dividing Eq. (i) by Eq. (ii), we get
$M w_{A} = 232$

Suggest Corrections

Similar questions

Q. 1.4 g of acetone dissolved in 100 g of benzene gave a solution which freezes at 277.12 K. Pure benzene freezes at 278.4 K. 2.8g of solid (A) dissolved in 100 g of benzene gave a solution which froze at 277.76 K. Calculate the molecular mass of (A).

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 ?

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. Pure benzece freezes at

{5.45}^{o} C

at a certain place but a

0.374

m solution of tetrachlororthane in benzene freezes at

{3.55}^{o} C

.The

K_{f}

for benzene is-

Join BYJU'S Learning Program