Question

How to calculate the mass of oxygen in 2.8 litres of CO2 at STP?

Answer 1

Molar volume for any gas at STP is 22.4 L
So,no. of moles of CO2 is 2.8/22.4
Now there are 2 moles O atoms per mole CO2 molecule , So No. of mole of O atoms is
2×2.8/22.4
Now mass of O is 16×2×2.8/22.4=4g

Answer 2

The mass of oxygen is 4 gram.

Explanation:

To calculate the mass of oxygen in 2.8 liters of $CO_2$ at STP, we will use the concept of Avogadro’s law.

We are aware of the fact that the volume of gas is 22.4 L at STP.

Therefore, No. of moles of CO_2 $=\frac{2.8}{22.4}$

Also, there are 2 moles of oxygen atoms per mole of $CO_2$ molecule, thus, the number of moles of O atoms $=2 \times \frac{2.8}{22.4}$

Therefore, Mass of O = $16 \times 2 \times \frac{2.8}{22.4}$ = 4 grams