Can you explain slide #44? I didn't understand the second proportion (how 1 mol H2 is equal to 2 mol HCl).
Again, 1 mole of H2 reacting with 1 mole of Cl2 produces 2 moles of HCl, you can see this from the balanced equation. It's a mathematical ratio. For every mole of H2, assuming you have enough Cl2 to react with it, you can produce 2 moles of HCl.