What is an ideal gas?

What are macroscopic quantities and microscopic quantities?

According to the kinetic theory of gases,at absolute temperature

Molecules of a gas behave like

What are the characteristics of the molecular model of an ideal gas according to the kinetic theory of gases?

Modern vacuum pumps can evacuate a vessel down to a pressure of $4.0 \times 10^{-15} \, atm$ at room temperature $(300 \, K)$. Taking $R = 8.0 \, J \cdot K^{-1} \cdot mol^{-1}$,$1 \, atm = 10^5 \, Pa$,and $N_A = 6 \times 10^{23} \, mol^{-1}$,the mean distance between molecules of gas in an evacuated vessel will be of the order of: