Can anyone come up with a nice easy step by step for this equation?

Question

3NO2(g) + H2O(l) ---- 2HNO3(aq) + NO(g)

Calculate the mass of nitric acid, HNO3, that could be made from 100g of nitrogen dioxide, NO2

Relative atomic masses H=1 N=14 O=16

I need to be able to explain this to a 14 year old science student, I have worked out the answer to be 91.35, but I would appreciate it if someone could explain the process of working this out in a simple(ish) easy step by step way that the student might understand (not my crazy rambling way :).

thank very much.

Answer 1

Simply explain that for every 3 moles of NO2, 2 moles of HNO3 are produced.

A ratio of 3:2, or 1 : 2/3

Now you have to calculate how many moles you have (of the limiting reagent NO2):

Moles = Mass / Mr

Moles = 100 / (14 + 2(16))

Moles = 2.17391304

Now refer back to the ratio..

1 : 2/3

2.17391304(1) : 2/3 * (2.17391304) [its multiplied by a common factor]

Since a single mole of NO2 produces 2/3 moles of HNO3; 2.17391304 would produce 2/3 * (2.17391304) moles of HNO3 (1.44927536mol)

Now to calculate the mass (of the desired produce) you use:

Mass = Moles * Mr

Mass = 1.44927536 * (1 + 14 + 3(16))

Mass = 91.3043478g