Question

How do you decide when to use this equation; $pV=nRT$ ?

Answer 1

This equation of ideal gas is used in relation with the other gas laws i.e. under the conditions of constant temperature, pressure ,volume of the gas and number of moles of the gas at standard conditions of temperature and pressure. Now you can easily answer the given statement.

Complete Solution :
The equation $pV=nRT$ is an ideal gas equation.
- Here p represents pressure of the gas in pascal , V represents the volume of the gas in liters, n represents the no. of moles of the gas, R is the gas constant and T is the temperature of the gas in kelvin.
The equation of the ideal gas i.e. $pV=nRT$ is used in those conditions when either temperature, volume or pressure of a gas are constant.
- In other words, we can say that this equation or the law is used in combination with the other laws of the gas i.e. Boyle’s law ( when temperature is constant), Charles’s law 9 when pressure is constant) , Gay-Lussac’s law ( when volume is constant), Avogadro’s law ( it states that at standard conditions of temperature and pressure one mole of the gas occupies the volume of $22.4L$ and contains Avogadro number of particles i.e. $6.023\times {{10}^{23}}$) etc.
- This law can also be used in those situations when out of the four properties i.e. pressure, volume, number of moles and temperature of the gas , three properties of a gas are given.

Note: Don’t get confused in the ideal and real gases. Ideal gases are those gases which obeys the gas laws at all conditions of the temperature and pressure . On the other hand, real gases are gases which obey the gas law at standard conditions of temperature and pressure i.e. at 1 atmosphere pressure and $273K$ temperature.