Question

a mixture contain .2gm of oxygen gas and .4g ofcarbon dioxidegas.the ratio of oxygen atoms present in oxygen gas tocarbon dioxidegas

Answer 1

Mass of Oxygen gas = 2 g
Mass of CO₂ = 4 g
Molar mass of O₂ gas = 32 g mol^-1
Molar mass of CO₂ gas = 44 g mol^-1
​32 g of O₂ contains 6.022 $\times$ 10²³ molecules
1 molecule of O₂ contains 2 atoms
32 g of O₂ contains 2$\times$6.022$\times$10²³ atoms
2 g of O₂ contains (2$\times$6.022$\times$10²³/ 32)$\times$2
= 6.022$\times$10²³ / 8 atoms
Similarly, 44 g of CO₂ contains 2$\times$6.022$\times$10²³ atoms of Oxygen ( 1 molecule of CO₂ contains 2 atoms of oxygen)
4 g of CO₂ contains ​(2$\times$6.022$\times$10²³/ 44)$\times$4
= ​2 $\times$6.022$\times$10²³ / 11 atoms of Oxygen

Ratio of Oxygen atoms in oxygen to oxygen atoms in CO₂ = ​ 6.022$\times$10²³ / 8 : ​2 $\times$6.022$\times$10²³ / 11
= 11 : 16