1. Lecture 60 Defining Stoichiometry Ozgur Unal
NIS – CHEMISTRY
Lecture 60
Defining Stoichiometry
Ozgur Unal

2. Defining Stoichiometry
The study of quantitative relationships between the amounts of reactants used and amounts of products formed by a chemical reaction is called stoichiometry.
Example: 4Fe (s) + 3O2 (g)  2Fe2O3 (s)
4 moles of Fe reacts with 3 moles of O2 to produce 2 moles of Fe2O3.
223.4 g of Fe reacts with 96 g of O2 to produce g of Fe2O3.
As you can see the tota lmass is conserved  law of conservation of mass
mass of reactants = mass of products

3. Mole Ratios
A mole ratio is a ratio between the numbers of moles of any two of the substances in a balanced chemical equation.
Moles ratios are useful in calculating the amounts of substances involved in a chemical reaction.
Example: 2K (s) + Br2 (l)  2KBr (s)
Mole ratios:
2 mol K / 1 mol Br2 and 2 mol K / 2 mol KBr
1 mol Br2 / 2 mol K and 1 mol Br2 / 2 mol KBr
2 mol KBr / 2 mol K and 2 mol KBr / 1 mol Br2
These six ratios define all the mole relationships in this equation.

4. Mole Ratios
Example: Determine all possible mole ratios for the following balanced chemical equations:
4Al (s) + 3O2 (g)  2Al2O3 (s)
3Fe (s) + 4H2O (l)  Fe3O4 (s) + 4H2 (g)
2HgO (s) +  2 Hg (l) + O2 (g)