How many molecules (not moles) of NH3 are produced from 1.72×10−4 g of H2?

Answer 1

Hi Layanne,

To find the molecules of NH₃, you need to convert grams of H₂ to moles of H₂ to moles of NH₃ to molecules of NH₃, and this can easily be done using dimensional analysis, where the units are treated as variables that can be cancelled out.

First, we need a formula. Which I will write as a synthesis reaction and balance the reaction:

3H₂+N₂=2NH₃

In one straight expression, you would write it out as:

1.72*10^-4 g H₂ * 1 mol H₂/2.016 g H₂ * 2 mol NH₃/3 mol H₂ * 6.023 * 10²³molecules NH₃/ mol NH₃ = 3.43*10¹⁹ molecules NH₃

Its a bit of a jumble, but you'll find that all units cancel out except for molecules of NH₃. If you want a more detailed explanation of dimensional analysis or the process by which I got these numbers, I can explain them in the comments.