Balancing equations using oxidation numbers C3H8O + CrO3+ H2SO4→Cr2(SO4)3+ C3H6O + H2OReview: balancing chemical equations• Balance the following chemical reaction:CuCl2+ Al →Cu + AlCl3• In the past (e.g. in grade 11) we balanced equations by “inspection”.• Balancing equations relied on having equal numbers of atoms on each side of the equation• We can balance equations using oxidation #s.• This relies on the idea that the number of electrons lost by an element must be equal to the number gained by a different element.• In other words the total gain in oxidation numbers must be equal to the total lost.Using Oxidation Numberstotaloxidation #CuCl2+ Al →Cu + AlCl3• Notice: Cu has gained 2e–(oxidation # ↓by 2)• Notice: Al has lost 3e–(oxidation # ↑by 3)• But, number of e–gained must equal e–lost• Multiply Cu by 3, Al by 2: change is 6 for bothchangetotaloxidation #3CuCl2+ 2Al →3Cu + 2AlCl3-1-2+2+20000+3+3 -3-1-1-2+2+20000+3+3 -3-1+600+6+6-6Steps to balancing equations1. Write the skeleton equation2. Assign oxidation numbers to all atoms
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This note was uploaded on 04/12/2011 for the course CHEM 1010 taught by Professor Marshall during the Spring '11 term at North Texas.