A solution of benzene and toluene at 25 °C exerts a total vapor pressure of 66.6 torr. What is the mole fraction of benzene in the vapor phase? The vapor pressures of pure benzene and toluene at 25 °C are 94.2 torr and 28.4 torr, respectively. 0

0.5805.

Explanation:

Using Raoult's Law;

Psol = Xbenzene * P°benzene + Xtoluene * P°toluene

where,

Psol = vapor pressure of the solution

Xbenzene = mole fraction of benzene

P°benzene = vapor pressure of pure benzene

Xtoluene = mole fraction of toluene

P°toluene = vapor pressure of pure toluene

Mole fraction is defined as the ratio between the number of moles of a component in a solution to the total number of moles in the solution.

Xbenzene + Xtoluene = 1

Let,

Y = mole fraction of toluene

X = mole fraction of benzene

X = 1 − Y

Psol = X * P°benzene + (1 − X) * P°toluene

66.6 = X * 94.2 + (1 − X) * 28.4

X = 0.5805

Therefore,

Y = 1 - 0.5805

= 0.4195

Mole fraction of benzene = 0.5805.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.