Question

One atmospheric pressure (atm) is equal to
A. 101325 Pa
B. 1013.25 Pa
C. 101.325 Pa
D. 10.1325 Pa

Answer 1

Hint: One bar is equal to the atmospheric pressure at the average sea level and at $g=9.8$$m{s}^{-2}$, where, g is the acceleration due to gravity. There are other units of pressure like bar and dyne.

Formula used: 1 bar $={10}^5$Pa and 1 atm $=1.01325$bar.

Complete step by step answer:
The SI unit of pressure is pascal. and one pascal is equal to 1 newton force applied on an area of 1 $m^2$.
Now, we know that $1$ bar $={10}^5$Pa…(1)
We also know that 1 atm $=1.01325$bar…(2)
From equation (1) and (2), we can easily get
1 atm $=1.01235\times {10}^5$Pa
Or
1 atm$=101325$Pa.

So, the correct answer is “Option A”.

Additional Information: The atmospheric pressure occurs when earth pulls the gases towards itself due to its gravitational pull.
1 atm is the pressure at the average sea level. At the different points, the value of atmospheric pressure varies.
The atmospheric pressure is measured by a barometer.
The pressure of a gas is measured by a device called a manometer.
The home barometers measure the atmospheric pressure with reference to average sea level.
Barometers are used for weather forecasting, and predicting natural calamities caused in air, like cyclones and tornadoes.
Surface pressure is atmospheric pressure on the earth’s surface, it may or may not be equal to the atmospheric pressure.
As we go higher in altitude, the atmospheric pressure decreases.
Our blood pressure balances the atmospheric pressure.
People living on higher altitudes have lower average blood pressure levels.
A thermodynamic process, in which the pressure of initial and final state remains the same is called an isobaric process.
The boiling point of a liquid is the temperature at which the vapor pressure of the liquid becomes equal to the atmospheric pressure.
When the atmospheric pressure of the surrounding drops, the boiling point of water drops, e.g. in hilly areas.
The lower the surface area, the higher is the pressure, that is why the cutting ends of knives are sharper.

Note: At 1 atm pressure, the height of mercury in a capillary is generally considered 76 cm. Some students might confuse 1 atmospheric pressure as 76 or 760, but they must keep in mind that 76 cm or 760 mm is the height of mercury, it is length not pressure.