Supplemental packet page 117

This is a chemical recipe for the decomposition of water by electrolysis. productsreactants 1. Chemical reactions involve just the simple rearrangement of atoms. 2. Atoms are conserved in a chemical reaction. In other words, atoms are not created nor destroyed in chemical reaction. Is this true for the above decomposition of water by electrolysis? What did John Dalton in 1808 have to say about reactions?

What are the physical states of these substances at 25°C (room temp)? (l)(g) Did you guess that twice the volume of gas of H 2 should be produced in relationship to the amount of O 2 gas produce? two molecules : one molecule hydrogen gas oxygen gas Physically, predict what one might observe if this reaction were to occur. two molecules of water 4 hydrogen atoms 2 oxygen atoms

(l)(g) Since this reaction needs electrons,, Addition of a battery will make it go. Addition of collection tubes will allow us to collect the gases.

(l)(g) two molecules : one molecule hydrogen gas oxygen gas Since this reaction needed electrons from a battery to make it go, this reaction is regarded as an oxidation-reduction. REDOX for short. HUH? Which column contains hydrogen gas?

(l)(g) REDOX, is about the exchange of electrons. H+H+ H

Reduction is Gain, RIG (l)(g) 00 2H + + 2e - H 2 0 The battery supplies those electrons Remember hydrogen ions’s favorite charge in its combined state is: H +

(l)(g) Then what happened the oxygen atom in water? 00 So oxide ion must have lost electrons O 2- O 0 + 2e - Lost electrons in the electrolysis are attracted To the positive ca hode Oxidation is loss of electrons, OIL Remember oxygen ion’s favorite charge in its combined state is: O 2- 2-

O 2- O 0 + 2e - 2H + + 2e - H 2 0 Oxidation is Loss, OIL Reduction is Gain, RIG REDOX, is about the exchange of electrons. Summary: