What volume of no2 can be produced from 15 dm^3 of nitrogen and 20 dm^3 of oxygen if all three gases are at the same temperature and pressure?

Question

I'm just confused about how to get started. I converted dm^3 to L and found out the mol of each element, using the ideal gas law. and got 183 mol of n and 244 mol of O. then I multiplied 183 by the ratio of 2 mol O/1 mol N. But that isn't the correct answer.

any help would be appreciated

Answer 1

N2 (g) + 2O2 (g) ---------------- 2NO2 (g)

1 mole 2moles 2 moles Applying Avogador's Law

1dm3 2dm3 2dm3

!dm3 of N2 reacts with 2dm3 of O2 so

15 dm3 of N2 need to react with 30 dm3 of O2

However there are only 20 dm3 of O2 available, so O2 in this reaction is limiting reactant, hence it will determine the volume of NO2 produced.

2 dm3 of O2 produce 2dm3 of NO2 so

20 dm3 of O2 will produce 20 dm3 of NO2

Answer= 20 dm3 of NO2

Answer 2

Whenever you have all gases or you are doing stoichiometry from gas to gas, use Avogadro's Principle that moles is proportional to volume :

N₂ + 2O₂ → 2NO₂ is the balanced equation.

This is a limiting reactant problem: You need twice as much oxygen as nitrogen in moles or volume. You have 1.33 times the oxygen, so oxygen is the LR.

20 liters of O₂ (2 liters of NO₂/2 liters of O₂) = 20 liters of NO₂