Pure water freezes at 273 K and 1 bar. The addition of 34.5g of ethanol to 500g of water changes the freezing point of the solution. Use the freezing point depression constant of water as 2K kg $m o l^{- 1}$ . The figures shown below represent plots of vapour pressure (V.P.) versus temperature (T). [Molecular weight of ethanol is 46g $m o l^{- 1}$ ]
Among the following, the option representing change in the freezing point is

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Solution

The correct option is A
$- Δ T_{f} = i k_{f} m_{2})$
$= 1 \times 2 \times \frac{34.5}{46 \times 500} \times 1000 = 3$
Vapour pressure curves shown in (b) is in agreement with the calculated value of $- Δ T_{f}$ . (a) is wrong as vapour pressure decreases on cooling.

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Similar questions

Q. Pure water freezes at 273 K and 1 bar. The addition of 34.5g of ethanol to 500g of water changes the freezing point of the solution. Use the freezing point depression constant of water as 2K kg

m o l^{- 1}

. The figures shown below represent plots of vapour pressure (V.P.) versus temperature (T). [Molecular weight of ethanol is 46g

m o l^{- 1}

]
Among the following, the option representing change in the freezing point is

Q. Pure water freezes at

273 K

and

1 bar

. The addition of

34.5 g

of ethanol to

500 g

of water changes the freezing point of the solution. Use the freezing point depression constant of water as

2 {K kg mol}^{- 1}

. The figures shown below represent plots of vapour pressure (V.P.) versus temperature

(T)

. (Molecular weight of ethanol is

46 {g mol}^{- 1}

). Among the following, the option representing change in the freezing point is:

Properties such as boiling point, freezing point and vapour pressure of a pure solvent change when solute molecules are added to get homogeneous solution. These are called colligative properties. Applications of colligative properties are very useful in day-to – day life.

One of its examples is the use of ethylene glycol and water mixture as anti-freezing liquid in the radiator of automobiles.

A solution M is prepared by mixing ethanol and water. The mole fraction of ethanol in the mixture is 0.9.

Given, freezing point depression constant of water

$(K_{f}^{w a t e r}) = 1.86 K k g m o l^{- 1}$