Question

Which of these options is equal to $1\,atm$?
A. $780\,torr$
B. $760\,torr$
C. $750\,torr$
D. $790\,torr$

Answer 1

Hint: Atmospheric pressure is the force exerted on the ground by the air above it when it is attracted to earth by gravity. Usually atmospheric pressure is measured with a barometer. It is represented by the unit atmosphere. It can also be visualised on the earth’s surface as a column above the surface, reaching all the way to the top of the atmosphere.

Complete step by step solution:
The pressure exerted by air in the atmosphere at the earth’s surface is maximum and reduces as the altitude increases. The explanation for this is that at sea level the density and volume of the atmosphere is highest and decreases with rising altitude. Also, the air molecules are less in number at a high altitude as compared to air molecules at low altitude.
Barometric height is used as a measurement to express the atmospheric pressure and air pressure retaining mercury in the container, so mercury height is used as a unit to reflect the atmospheric pressure.
$P = \rho gh$, where $P = $ pressure, $\rho = $ density of liquid, $ g = $ gravity and $h = $ height. This expression is used to measure barometric pressure or height. We can compute the height by understanding the atmospheric pressure.
We should multiply the pressure by the conversion factor to convert an atmosphere to the torr unit. One atmosphere is equivalent to $760\,torr $, so to convert we can use this basic formula-
Torr= atmospheres $ \times 760 $

Torr pressure is equal to atmosphere multiplied by $ 760 $.
Hence, option B is correct.

Note:
Torr= atmospheres $ \times 760$
We can also calculate atmosphere from the given formula. Also we should not be confused by pressure and atmospheric pressure as the units for pressure and atmospheric pressure are different.