What is the vapor pressure at 20 °c of an ideal solution prepared by the addition of 7.38 g of the nonvolatile solute urea, co(nh2)2, to 56.9 g of methanol, ch3oh? the vapor pressure of pure methanol at 20 °c is 89.0 mm hg.

a. 5.75 mm hg

b?

83.24 mmHg.

Explanation:

where, Psolution is the vapor pressure of the solution,

Xmethanol is the mole fraction of methanol,

P°methanol is the pure vapor pressure of methanol.

Xmethanol = (n)methanol/(n) total.

where, n methanol is the no. of moles of methanol.

n total is the total no. of moles of methanol and urea.

n of methanol = mass/molar mass = (56.9 g)/(32.04 g/mol) = 1.776 mol.

n of urea = mass/molar mass = (7.38 g )/(60.06 g/mol) = 0.123 mol.

∴ Xmethanol = (n)methanol/(n) total = (1.776 mol)/(1.776 mol + 0.123 mol) = 0.935.

∴ Psolution = (Xmethanol)(P°methanol) = (0.935)(89.0 mmHg) = 83.24 mmHg.

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.