Question

How can gas pressure be changed?

Answer 1

Variables like temperature, volume, pressure and no. of gaseous molecules (or no. of moles) are inter related to each other by various gaseous laws and hence all these factors will play an important role in changing the pressure of a gas.

Complete answer:
Let’s begin with the discussion of ideal gas equation:-
The variables like volume, temperature, pressure, and amount of a gas can be combined into the ideal gas law which can be written as follows:-
$PV=nRT$
The ideal gas law is the equation of state for an ideal gas (hypothetical). It is a good approximation of the behavior of many gases under certain conditions. It is a combination of the empirical Charles's law, Boyle's law, Avogadro's law, and Gay-Lussac's law.
Now, with the help of these laws, we will list down the factors affecting the pressure of a gas:-
-Volume of the gas:-
Pressure is affected by the volume of the container. If we decrease the volume of a container, the gas molecules have less space to move around. As a result, they will strike the walls of the container more often and thereby, pressure of the gas increases. And, if we increase the volume of a container, the gas molecules have more space to move around. As a result, they will strike the walls of the container less often and thereby, pressure of the gas decreases. This implies that pressure is inversely proportional to the volume of the container at constant temperature and amount of gas which is also known as Boyle’s law.
- Temperature of the gas:-
As the temperature is increased, the kinetic energy of gaseous molecules increases due to which they strike more often to the walls of the container and hence, pressure of the gas is increased. Similarly if we decrease the temperature, the pressure of the gas decreases certainly which implies that pressure is directly proportional to the absolute temperature of the gas at constant volume and amount of gas which is also known as Gay Lussac’s Law.
-Amount of gas:-
If we increase the amount of gas in a container, more no. of molecules strike to the walls of the container, hence increasing the pressure whereas if we decrease the amount of gas, less no. of molecules strike to the walls of the container which will ultimately decrease the pressure of the gas. Therefore at constant volume and temperature, pressure is directly proportional to the amount of gas.

Note:
Whenever you are asked about factors affecting any of the following variables: Temperature, pressure, no. of moles or volume of the gas, preferably answer it with the help of an ideal gas equation.