stoichiometry. law of conservation of mass antoine lavoisier studied combustion showed it involved...
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SToichiometrySToichiometry
Law of Conservation of
Mass
Antoine LavoisierStudied combustion
Showed it involved oxygen&life is supported by oxygen
in a process similar to combustion
Carefully weighted reactants & products
In an (ordinary) chemical reaction, mass is neither created nor destroyed.
Wrote first modern chemistry book
Worked as a tax collector during French RevolutionConsidered enemy of the peopleSent to guillotine
Law of Conservation of MassAll atoms you start with you end up with
Need to show conservation of mass with balanced equation
Reactant + Reactant --> Product
Combustion:Burning in the presence of oxygen
Heat is evolvedCombustion of hydrocarbonProduces CO2 & Water
Combustion:It is usually easiest to balancecarbon first
hydrogen secondcount how many oxygen needed in products
C5H12 + O2 --> H2O + CO256Need 16 oxygen for products
8
Mass-Mass & Mole-Mole Relations in ReactionsSuggested method:
1. write balancedequation
CO + 2 H2 --> CH3OH2. Make Chart
Grams
Molar Mass
Moles have
Given 100.0 g of each reactant,a. which is limiting reactant
b. how much of reactant in excess is leftc. How much product, in grams
100.0 g 100.0 g
28.0 g/mol 2.00 g/mol
______ ______/
//
/
3.57 mol 50.0 mol
3. Pick onetake moles have
& divide by balanced coefficient
This gives you a ratioto multiply other
coefficients by
3.57/1 = 3.57
Moles use 3.57 mol4. Take answer from step 3 multiply other
coefficient by it
3.57 x 2 = 7.14
7.14 mol
Moles left
- -
0 42.9 mol
Grams left 0 85.8 g
3.57 x 1 = 3.57
3.57 mol
32.0 g/mol
114. g
CO85.8 g
114. g
Theoretical yieldPercent yield = (actual yield/ theoretical yield) 100Let’s say you got 100.0 g for this reaction
Percent yield = (100.0 g / 114. g) 100 = 87.7 %
You might have your own method for You might have your own method for stoichiometry--that’s fine too.stoichiometry--that’s fine too.
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