Question

The molecular weight of gas A is 10 times greater than the molecular weight of gas B . These two gases are taken in cylinders of 5L volume at 1 atm pressure and ${27}^{o}C$. Comment on the number of molecules in the two gases. Justify with respect of kinetic molecular theory of gases.

Answer 1

Definition of mole

• The amount of substance that contains as many particles or entities(atoms, molecules or ions), as there are atoms exactly 12g of Carbon-12 isotope.
• A mole represents 6.022$\times$10²³.

Number of molecules N = $\frac{Numberofmoles}{AvogadroNumber}$

$N=\frac{n}{NA}$

Molecular weight of gas A = M_A

Molecular weight of gas B = M_B

Volume V = 5L

Pressure P = 1atm

$$\begin{gathered} T={27}^{o}C \\ =27+273 \\ =300k \end{gathered}$$

According to gas law ,

$$\begin{gathered} Pv=nRT \\ \therefore n=\frac{PV}{RT} \\ n=\frac{1x5}{0.82x300}=0.20 \\ NumberofmoleculeN=\frac{n}{N_A} \\ N=\frac{0.20}{6.022x{10}^{23}} \\ N=0.20x6.022x{10}^{-23} \end{gathered}$$