00:01
To estimate the change in energy associated with the formation of two moles of ammonia from hydrogen gas and nitrogen gas, we can use bond energies.
00:12
First, it's helpful to draw the lewis structure so we know what bonds we are working with.
00:18
The reaction is one mole nitrogen, which is a triple bond between two nitrogen atoms, with three moles of hydrogen, h2.
00:27
Each h2 molecule has one single hh bond, and then there's two moles of ammonia.
00:35
Each ammonia has three single hn bonds for a total of six hn bonds.
00:42
If the energy associated with the nn triple bond is 496, and we're only going to break one of these, one mole of these bonds, then it will require 496 kilojoules.
01:00
Next it asks you, well it tells you if the bond energy for hh is 432 kilojoules, how much energy is needed to break all three moles of the h -h bonds.
01:12
It'll just be three times 432 kilojoules per mole or 1 ,296 kilojoules...