1. Combustion Analysis
A g sample composed of C, H, N is burned to produce g CO2 and g H2O
Assume all C in the sample is converted to CO2
Assume all H is converted to H2O
To solve:
All C CO2, all HH2O (N is remainder)
Convert g CO2 to moles CO2 then find moles C
Convert g H2O to moles H2O, then find moles H
-gN = 1 1

2. Limiting Reactants Reactant that is “used up” in a chemical reaction
Excess reactant – reactant that is left over
Given amounts of more than one reactant
2 ways to solve:
Find the moles of each reactant, compare to moles in the reaction
Solve the problem twice (with each reactant), the reactant that produces the smallest amount is limiting 2 2

3. Why Use Excess Reactant?
Can cause the reaction to go faster
Use the least expensive as the excess
Can shift the reaction towards the products
Equilibrium reaction – reversible reaction 3 3

4. Yield Theoretical yield = calculated amount of product
Use stoichiometry
Experimental yield = actual yield
Amount obtained in a lab
Would be given in a problem “obtained”, “recovered”, etc.
Percent yield = experimental/theoretical x 100
Normally less than 100%
Incomplete reaction
Impure reagents
Experimental error
Side reactions 4 4