1. PROBLEM 4 OF LIMITING REAGENT SET
PROBLEM 4 OF LIMITING REAGENT SET. 4 Al + 3O2  2Al2O3 FIRST DETERMINE IF THERE IS A LIMITING REAGENT. FIND MOLES OF ALUMINUM METAL FIND MOLES OF OXYGEN GAS.
MOLES = MASS/GFM Al
MOLES = 2.5g Al/ 26.98g/mol
MOLES = mol Al
MOLES = MASS/GFM O2
MOLES = 2.5g O2 / 32.00g/mol
MOLES = mol O2
RATIO BOTH REACTANTS TO FIND LIMITING REAGENT.
O = mol O2
Al mol Al =
The actual ratio is larger than the theoretical, therefore the actual ratio fraction is too large, the denominator is to small Al is limiting.

2. 4 Al + 3O2  2Al2O3
STEP 1 Identify known (the substance that can be converted to moles), choose the correct equation to convert to moles.
MOLES = MASS/GFM Al
MOLES = 2.5g Al/ 26.98g/mol
MOLES = mol Al
STEP 2 RATIO known to objective,
Al = = ,
Al2O X X = mol Al2O3
STEP 3 Convert Objective to required units.
% yield = experimental/theoretical
3.5 / =74%
MOLES = MASS/GFM Al2O3
.0463 mol= mass/
Mass = g Al2O3