Chapter 9 NotesPart I

Mole to Mole Calculations

Balancing Equations Mini-Review

Mg + HCl → MgCl2 + H2

H2 + N2 → NH3

Al2O3 → Al + O2

Stoichiometry

Stoichiometry means using balanced equations to calculate quantities of chemicals used in a chemical reaction

A chemical equation is like a recipe; it shows you how

much of each “ingredient” is used and how much product

you will have in the end.

N2 + 3H2 2NH3

N2 + 3H2 2NH3

How many molecules of N2 are there?

N2 + 3H2 2NH3

How many molecules of N2 are there? 1

N2 + 3H2 2NH3

How many molecules of N2 are there? 1

How many molecules of H2 are there?

N2 + 3H2 2NH3

How many molecules of N2 are there? 1

How many molecules of H2 are there? 3

N2 + 3H2 2NH3

How many molecules of N2 are there? 1

How many molecules of H2 are there? 3

How many molecules of NH3 are there?

N2 + 3H2 2NH3

How many molecules of N2 are there? 1

How many molecules of H2 are there? 3

How many molecules of NH3 are there? 2

N2 + 3H2 2NH3

So one molecule of N2 will react with 3 molecules of H2 to form 2 molecules of NH3.

N2 + 3H2 2NH3

You could also say that one mole of N2 will react with 3 moles of H2 to form 2 moles of NH3.

The heart of stoichiometry is using a

balanced chemical equation as a

conversion factor for dimensional analysis.

Zn + HCl ZnCl2 + H2

For the above reaction, how many moles of zinc chloride can be produced with 0.27 moles of zinc?

Zn + HCl ZnCl2 + H2

For the above reaction, how many moles of zinc chloride can be produced with 0.27 moles of zinc?

Balance the equation first!!!

Zn + 2 HCl ZnCl2 + H2

For the above reaction, how many moles of zinc chloride can be produced with 0.27 moles of zinc?

Balance the equation first!!!

Zn + 2 HCl ZnCl2 + H2

For the above reaction, how many moles of zinc chloride can be produced with 0.27 moles of zinc?

0.27 moles Zn x 1 mole ZnCl2 = 0.27 moles ZnCl2

1 mole Zn

Zn + 2 HCl ZnCl2 + H2

For the above reaction, how many moles of zinc will react with 1.39 moles of hydrochloric acid?

Zn + 2 HCl ZnCl2 + H2

For the above reaction, how many moles of zinc will react with 1.39 moles of hydrochloric acid?

1.39 moles HCl x 1 mole Zn = 0.695 moles Zn

2 moles HCl

Na + H2O NaOH + H2

Using the above equation, if we started with 0.15 moles of sodium metal, how many moles of hydrogen gas was produced?

2 Na + 2 H2O 2 NaOH + H2

Using the above equation, if we started with 0.15 moles of sodium metal, how many moles of hydrogen gas was produced?

0.15 moles Na x 1 mole H2 = 0.075 moles H2

2 moles Na

Why are mole/mole problems impractical in a

laboratory setting?

Why are mole/mole problems impractical in a

laboratory setting?

We don’t measure directly in moles!

Why are mole/mole problems impractical in a

laboratory setting?

We don’t measure directly in moles!

Balances measure in grams.