Question

How many air molecules are present at room temperature $ ({27^\circ }C) $ , $ 1atm $ pressure?

Answer 1

Hint: In order to this question, to know the air molecules that are present at room temperature of given pressure, we will first convert the given temperature into Kelvin and then apply Ideal Gas Law.

Complete step by step solution:
Given temperature $ = {27^\circ }C = 300K $
And Pressure $ = 1atm $
Now, from the ideal gas law- $ PV = nRT $ , we have:
 $ \because \dfrac{n}{V} = \dfrac{P}{{RT}} = \dfrac{{1atm}}{{0.082\dfrac{{L \times atm}}{{mol \times K}} \times 300K}} = 0.046\dfrac{{mol}}{L} $
Since $ 1mol = 6.02 \times {10^{23}}molecules $
So, we will have $ 2.45 \times {10^{22}}molecules/L $ .

Note:
An ideal gas contains molecules of a negligible size that have an average molar kinetic energy that depends only on temperature. Intermolecular forces and molecular size are not considered by the Ideal Gas Law. The Ideal Gas Law applies best to monatomic gases at low pressure and high temperature.