Stoichiometry Chapter 9

Stoichiometry In this chapter, we will revisit the mole concept and use it to relate quantities of reactants & products.

Stoichiometry What is stoichiometry? Outside world connections – cooking, manufacturing, etc. Interpreting balanced chemical equations

Stoichiometry What is stoichiometry? Chemical equation consists of reactants & products, coefficients are there to give # of particles involved (moles, molecules, formula units, atoms, etc.)

Stoichiometry What is stoichiometry? Chemical equation… Will later use coefficients from balanced equations to find actual amounts of substances (mass, volume, etc.)

Stoichiometry Example French Toast 3 eggs, slightly beaten 1 c milk ½ tsp salt 6 slices of bread 2 Tbs sugar

Stoichiometry Example French Toast The recipe makes 6 slices of French Toast. How would you make 12 slices? What is the ratio of eggs to bread? Did it change when the recipe was increased to make more servings? What would happen if you tried to make the recipe with only 1 egg?

Stoichiometry Example Following a recipe is a lot like performing a chemical reaction. You have to have the right reactants and enough of each one or things will not turn out as planned.

Stoichiometry… Just like in cooking, ratios are very important in balanced chemical equations.

Stoichiometry… What is the ratio of H2 to O2 in the following equation? 2 H2 + O2  2 H2O Would the ratio change if more water was produced? Why?

Beginning Stoich Verifying the law of conservation of matter Balanced eqs “obey” the law:

Beginning Stoich Verifying the law of conservation of matter Balanced eqs “obey” the law: 2 H2 + O2  2 H2O

Beginning Stoich Mole-mole problems Converting from moles of substance A to moles of substance B requires a mole ratio from the balanced chemical equation

Beginning Stoich Mole-mole problems Ex 1: A pink paint is produced by using 3 L of white & 1 L of red The paint ratio is ___ If we only want 2 L of pink paint what do we need? Mix ___ L white & ___ L red

Beginning Stoich Mole-mole problems Ex 2: NH4NO3  N2O + H2O Suppose we wanted to know the number of moles of product created by 2.25 moles ammonium nitrate

Beginning Stoich Mole-mole problems Ex 3: HCl + Zn  ZnCl2 + H2 How many moles HCl needed to react with 5.70 moles Zn?

Beginning Stoich Mole-mole problems Ex 4: N2O5 + H2O  HNO3 How many moles HNO3 produced from 0.51 moles N2O5?

Beginning Stoich Mole-mole problems Ex 5: Pb + HCl  PbCl2 + H2 How many moles HCl needed to react with 0.36 moles Pb?