SAQ : What is the number of molecules in 11.2 L of O2 at STP?

Question

What is the number of molecules in 11.2 L of O₂ at STP? [Ans. 3.011 × 10²³]

Answer

Step 1: Calculation of number of moles

moles of O₂ = Given Volume\ of\ O_2 \over 22.4

= 11.2 \over 22.4

= 0.5 mol

Step 2: Calculation of number of molecules

number of molecules of O₂ = moles of O₂ × Avogadro’s number

= 0.5 × 6.022 × 10²³

= 3.011 × 10²³ molecules

Therefore, the number of molecules in 11.2 L of O₂ at STP is 3.011 × 10²³ molecules.