Transcript Chemistry

Chemistry
Ch 12
Stoichiometry
Notes #1
What is stoichiometry?
• Study of quantitative relationships btwn
amounts of reactants used and products
formed by a chemical reaction
• Based on the law of conservation of
mass
• Chapter 11 math is the basis of the
chapter 12 math – if you don’t get it – ask!
Interpreting equations
• 4Fe (s) + 3O2 (g) -> 2Fe2O3 (s)
– Particles
• 4 atoms Fe react with 3 molecules of O2 to produce 2
formula units of Fe2O3
– Moles
• 4 mol Fe react with 3 mol of O2 to produce 2 mol of
Fe2O3
– Mass
• 223.4g Fe react with 96.0g O2 to produce 319.4g of
Fe2O3
• 319.4 = 319.4
Example - interpreting
• N2 (g) + 3H2 (g) -> 2NH3 (g)
– Particles
• 1 molecule N2 + 3 molecules H2 -> 2 molecules NH3
– Moles
• 1 mol N2 + 3 mol H2 -> 2 mol NH3
– Mass
• 28.02g N2 + 6.06g H2 -> 34.08g NH3
• 34.08g = 34.08 g
Homework
• Interpreting
• 6-14 on side 1 of sg
• Number 1 on the supplemental
• That much should be DONE for tomorrow!
Mole Ratios
• Ratio between the numbers of moles of
any 2 substances in a balanced
chemical equation
• We will be using mole ratios as
conversions factors in future math
problems
• Mole ratios show relationships between
reactants and products in equations
Example – Mole Ratio
• 2Al (s) + 3Br2 (l) -> 2AlBr3 (s)
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How many will there be?
Number of species x 1 less
Species = reactants and products
2 reactants + 2 Products = 4 species
4 x 3 = 12 mole ratios
Example – Mole Ratio
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What is the mole ratio with the biggest value?
What is the mole ratio relating Al to Br?
What is the mole ratio relating the product to Al?
HW – back of SG and #2 on supp