Composition Stoichiometry deals with the mass relationships of elements in compounds.

Reaction Stoichiometry

involves the mass relationships between

reactants and products in a chemical reaction.

All reaction Stoichiometry calculations start with a balanced chemical equation. This equation gives the relative numbers of moles of reactants and

products.

Reaction-Stoichiometry problems can be classified according to the information given in the problem and the information you are expected to find, the unknown.

The given and the unknown may both be reactants, they may both be products, or one may be a reactant and the other a product!

The masses are generally expressed in grams.

Stoichiometric problems are solved by using ratios from the balanced equation to convert the given quantity.

Given and unknown quantities are amounts in moles.

Road Map…

Given is an amount in moles and the unknown is a mass that is often expressed in grams.

Road Map…

Given is a mass in grams and the unknown is an amount in moles.

Road Map…

Given is a mass in grams and the unknown is a mass in moles.

Road Map…

Solving any reaction-stoichiometry problem requires the use of a mole ratio to convert from moles or grams of one substance in a reaction to moles or grams of another substance.

A mole ratio is a conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction.

This information is obtained directly from the balanced chemical equation.

2 3 22 ( ) 4 ( ) 3Al O l Al s O

2 32 3

413.0 26.0

2

mol Almol Al O x mol Al

mol Al O

Mole ratios are exact, so they do not limit the number of significant figures in a calculation. The number of

significant figures in the answer is therefore determined only by the number of significant figures of any measured

quantities in a particular problem.

Recall that the molar mass is the mass, in grams, of one mole a substance.

You will need to determine molar masses using the periodic table.

For Example:

2 3 22 3 2

2 3 2

2 3 2

101.

2 (

96 32.00 26.98

) 4 ( )

1

3

1 1& &

g Al O g O g AlAl O O Al

mol

Al O l Al s

Al O mol O m l Al

O

o

2 3 22 3 2

2 3 2

2 3 2

101.

2 (

96 32.00 26.98

) 4 ( )

1

3

1 1& &

g Al O g O g AlAl O O Al

mol

Al O l Al s

Al O mol O m l Al

O

o

26.9826 701

1

g Almol Al x g Al

mol Al

2HgO(s)→2Hg(l)+O₂(g)

4NH₃(g)+6NO(g)→5N₂(g)+6H₂O(l)

You will produce a multi-media file using SmartBoard software and your choice of technology to create a presentation of the 4 types of reaction-stoichiometry problems.

You are allowed to choose four of the problems from the sample problem sheet to use in your project.

You must include video and voice while describing how to problem solve each of the four types of problems.

Eye candy is important and you may work in pairs of two.

Finished projects must be uploaded to the SchoolWeb site by the end of class and be titled by students first names.