Question

Small amounts of oxygen gas can be produced in the laboratory from the decomposition of several different chemicals. If you have 10 g samples of each of these compounds, which would produce the largest mass of oxygen?

2NaNO3 ---> 2NaNO2 + O2

KClO4 ---> KCl + 2O2

2H2O2 ---> 2H2O + O2

2HgO ---> 2 Hg + O2

Answer 1

Molar mass of NaNO ₃ = 85 g/ mole.

10 g NaNO ₃ = 10/85 = 0.117 mole.

From the balanced equation,

2 mole NaNO ₃ produces 1 mole oxygen = 32 g Oxygen.

Hence mass of oxygen formed by 0.117 mole NaNO ₃ = 32*0.117/2 = 1.882 g.

Molar mass of KClO ₄ = 138.5 g/ mol

10 g KClO ₄= 10/138.5 mole.

From the balanced reaction,

1 mole KClO ₄ produces 2 mole oxygen = 2*32= 64 g oxygen.

Hence 10/138.5 mole KClO ₃ produces = 64*10/138.5 = 4.620 g oxygen.

Molar mass of H ₂ O ₂ = 34 g.

10 g H ₂ O ₂ = 10/34 mole

From balanced equation,

2 mole Hydrogen peroxide produces 1 mole oxygen = 32 g Oxygen.

Then, 10/34 mole will form = 10*32/2*34 = 4.705 g oxygen.

Molar mass of HgO = 216.6 g/mole

2 mole HgO produces 1 mole oxygen = 32 g oxygen. ( By balanced equation)

10 g HgO = 10/216.6 mole

Hence , 10/216.6 mole HgO produces = 32*10/2*216.6 = 0.738 g oxygen.

Therefore, 10 g H ₂ O ₂ will produce the largest mass of oxygen.