80) Which one of the following should have the lowest boiling point? Group of answer choices HCl H2S PH3 H2O SiH4

SiH4

Explanation:

We must remember that the magnitude of intermolecular forces play a vital role in the determination of the boiling point of a substance.

The Si-H bond is the least polar among all the bonds in compounds listed in the question. This is because the electronegativity difference between silicon and hydrogen is very slim resulting in the formation of a nonpolar covalent bond.

The other compounds possess more polar bonds hence have a greater degree of dipole interaction between molecules and a consequently higher boiling point than SiH4.

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.

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