Carbon-12 is the most common isotope of carbon and has a mass number of 12. However

the average atomic mass of carbon found on a periodic table is slightly more than 12 Daltons.

Explanation:

Isotope refers to each of two or more forms of the same element that contains the same number of protons but a different number of neutrons. Isotopes differ with respect to relative atomic mass.

Carbon is a non-metal having atomic number 6 and has two main forms diamond and graphite. It also occurs in impure forms charcoal, soot, and coal.

Carbon-12, Carbon-13, Carbon-14 are naturally occurring isotopes of carbon.

Among these, Carbon-12 is the most common isotope of carbon such that it has a mass number of 12. However, the average atomic mass of carbon found on a periodic table is slightly more than 12 Daltons.

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.

the cold front replaces the warmer air at the ground level changing the wind to be breezy and denser.there is also an immediate drop in the temperature.