balancing-oxidation-numbers

# balancing-oxidation-numbers - C3H8O CrO3 H2SO4 Cr2(SO4)3...

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Balancing equations using oxidation numbers C 3 H 8 O + CrO 3 + H 2 SO 4 Cr 2 (SO 4 ) 3 + C 3 H 6 O + H 2 O

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Review: balancing chemical equations Balance the following chemical reaction: CuCl 2 + Al Cu + AlCl 3 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 Numbers total oxidation # CuCl 2 + Al Cu + AlCl 3 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 both change total oxidation # 3CuCl 2 + 2Al 3Cu + 2AlCl 3 -1 -2 +2 +2 0 0 0 0 +3 +3 -3 -1 -1 -2 +2 +2 0 0 0 0 +3 +3 -3 -1 +6 0 0 +6 +6 -6

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Steps to balancing equations 1. Write the skeleton equation 2. Assign oxidation numbers to all atoms 3. Identify which atoms change oxidation number 4. Make the number of atoms that change
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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.

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balancing-oxidation-numbers - C3H8O CrO3 H2SO4 Cr2(SO4)3...

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