Comprehension # 2
Following passage explains the effect of temperature on the vapour pressure of the liquid.

Effect of temperature on vapour pressure
The quantity of heat required to evaporate a given liquid at constant temperature is defined as the heat of vaporisation. Variation of vapour pressure with temperature is given by,

Clausius-Clapeyron equation.

$l o g_{e} P = - \frac{Δ H_{v a p}}{R T} + l o g_{e} A$

A liquid is said to be at its boiling temperature if its vapour pressure is equal to external pressure. Therefore, the boiling point of water in particular and of liquids in general decreases as an altitude of a place increases where the external pressure is less than $1 a t m o s p h e r e$ (normal b.p. of water is $373.15 K$ at $1 a t m o s p h e r e$ )

On top of mount everest, for example, where the atmospheric pressure is only about $260 m m H g$ , water boils at approximately $71^{\circ} C$ . Conversely, if the external pressure on a liquid is greater than $1 a t m$ , the vapour pressure necessary for boiling than normal boiling is reached later, and the liquid boils at a temperature greater than the normal boiling point.

Clausius-Clapeyron equation can be written in the following form:

P = A e^{- Δ H_{v a p} / R T}

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

\frac{d l o g_{10} P}{d T} = \frac{Δ H_{v a p}}{2.303 R T^{2}}

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

\frac{d l o g_{e} P}{d T} = - \frac{Δ H_{v a p}}{R T^{2}}

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

P = A e^{Δ H_{v a p} / R T}

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

Open in App

Solution

The correct options are
A $P = A e^{- Δ H_{v a p} / R T}$
B $\frac{d l o g_{10} P}{d T} = \frac{Δ H_{v a p}}{2.303 R T^{2}}$

Suggest Corrections

Similar questions

100^{\circ} C

{99.6}^{\circ} C

The variation of vapour pressure of different liquids with temperature is shown in fugure

(i) Calculate graphically boiling points of liquids A and B.

(ii) If we take liquid C in a closed vessel and heat it continuously. At what temperature will it boil?

(iii) At high altitude, atmospheric pressure is low (say 60 mm Hg). At what temperature liquid D boils?

(iv) Pressure coojer is used for cooking food at hill station. Explain in terms of vapour pressure why is it so?

Join BYJU'S Learning Program