# Chapter 9 Notes Part I Mole to Mole Calculations.

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Chapter 9 Notes Part I Mole to Mole Calculations

Balancing Equations Mini-Review Mg + HCl → MgCl 2 + H 2 H 2 + N 2 → NH 3 Al 2 O 3 → Al + O 2

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.

N 2 + 3H 2  2NH 3

How many molecules of N 2 are there?

N 2 + 3H 2  2NH 3 How many molecules of N 2 are there? 1

N 2 + 3H 2  2NH 3 How many molecules of N 2 are there? 1 How many molecules of H 2 are there?

N 2 + 3H 2  2NH 3 How many molecules of N 2 are there? 1 How many molecules of H 2 are there? 3

N 2 + 3H 2  2NH 3 How many molecules of N 2 are there? 1 How many molecules of H 2 are there? 3 How many molecules of NH 3 are there?

N 2 + 3H 2  2NH 3 How many molecules of N 2 are there? 1 How many molecules of H 2 are there? 3 How many molecules of NH 3 are there? 2

N 2 + 3H 2  2NH 3 So one molecule of N 2 will react with 3 molecules of H 2 to form 2 molecules of NH 3.

N 2 + 3H 2  2NH 3 You could also say that one mole of N 2 will react with 3 moles of H 2 to form 2 moles of NH 3.

The heart of stoichiometry is using a balanced chemical equation as a conversion factor for dimensional analysis.

Zn + HCl  ZnCl 2 + H 2 For the above reaction, how many moles of zinc chloride can be produced with 0.27 moles of zinc?

Zn + HCl  ZnCl 2 + H 2 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  ZnCl 2 + H 2 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  ZnCl 2 + H 2 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 ZnCl 2 = 0.27 moles ZnCl 2 1 mole Zn

Zn + 2 HCl  ZnCl 2 + H 2 For the above reaction, how many moles of zinc will react with 1.39 moles of hydrochloric acid?

Zn + 2 HCl  ZnCl 2 + H 2 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 + H 2 O  NaOH + H 2 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 H 2 O  2 NaOH + H 2 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 H 2 = 0.075 moles H 2 2 moles Na

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.