Answer: H₂O₂ (94%) > Air (23%) > Exhaled air (13%) > NaHCO₃ (0%)
Initial important note:
Although NaHCO₃ contents oxygen atoms, and you can calculate its compositoin, the resulting gas does not containg pure oxygen gas (O₂). For the comparisson it is not useful to calculate the content of oxygent atoms, but the concentration of O₂ gas. As such, the gas from NaHCO₃ contains 0% of pure O₂, that is why it is ranked last.
1) Air:
Source: internet
Approximate 23%. It is variable, because air is not a pure substance but a mixture of gases, whose compositon is not unique.
2) Exhaled air:
Source: internet.
Approximate 13%. The compositon of the air changes in our lungs, due to the respiration process: we inhale fresh air with around 23% of oxygen, part of this oxygen pass to the cells (lungs - blood - heart - cells) and then it is exhaled with a lower content of air and a greater content of CO₂
3) Air from the decomposition of H₂O₂.
In this case we can do a chemical calculation, since we can state the chemical equation of the reaction:
i) Chemical Equation:
H₂O₂ (g) → H₂ (g) + O₂ (g)
ii) mole ratio of the products 1 mol H₂ : 1 mol O₂
iii) convert moles into mass (grams)
1 mol H₂ × 2 × 1.008 g/mol = 2.016 g
1 mol O₂ × 2 × 15.999 g/mol = 31.998 g
Composition, % = [31.998 g / (2.016 g + 31.998 g) ] × 100 ≈ 94%
4) Air from the decomposition of NaHCO₃:
i) chemical equation:
2 NaHCO₃(s) → Na₂CO₃(s) + CO₂(g) + H₂O(g)
ii) mole ratio: take into account only the gases in the products:
1 mol CO₂ (g) : 1 mol H₂O
iii) mass in grams
CO₂: molar mass ia approximately 44.01 g/mol
H₂O: molar mass is approximately 18.02 g/mol
iii) Those gases although have oxygen atoms, do not hae free oxygen gas, which is what we are compariing. That means, that from the decomposition of NaHCO₃ you get 0% oxygen gas.
5) The result is:
H₂O₂ (94%) > Air (23%) > Exhaled air (13%) > NaHCO₃ (0%)
or
;
tells us that there is
number of molecules or atoms in 1 mole of substance. We need two conversion factors to convert the number of molecules to a mass: firstly, we need to convert the number of molecules into the number of moles using Avogadro's constant and then we need to use the molar mass to convert the moles obtained into mass.