Chapter 9 Notes IChapter 9 Notes I

StoichiometryStoichiometry

StoichiometryStoichiometry

Calculations of quantities in Calculations of quantities in chemical reactionschemical reactions

This means using balanced This means using balanced equations to calculate quantities equations to calculate quantities of chemicals used in a chemical of chemicals used in a chemical reactionreaction

A chemical equation is like a A chemical equation is like a recipe; it shows you how much recipe; it shows you how much of each “ingredient” is used and of each “ingredient” is used and how much product you will have how much product you will have

in the end.in the end.

NN22 + 3H + 3H22 2NH 2NH33

How many molecules of NHow many molecules of N22 are there? are there?

How many molecules of HHow many molecules of H22 are there? are there?

How many molecules of NHHow many molecules of NH33 are there? are there?

So one molecule of NSo one molecule of N22 will react with 3 will react with 3

molecules of Hmolecules of H22 to form 2 molecules of to form 2 molecules of

NHNH33..

You could also say that one mole of NYou could also say that one mole of N22 will will

react with 3 moles of Hreact with 3 moles of H22 to form 2 moles of to form 2 moles of

NHNH33..

The heart of stoichiometry is The heart of stoichiometry is using a balanced chemical using a balanced chemical equation as a conversion equation as a conversion

factor for dimensional analysis.factor for dimensional analysis.

Zn + HCl Zn + HCl ZnCl ZnCl22 + H + H22

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

Zn +2 HCl Zn +2 HCl ZnCl ZnCl22 + H + H22

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

Why are mole/mole problems Why are mole/mole problems impractical in a laboratory impractical in a laboratory

setting?setting?

4Fe + 3O4Fe + 3O22 2Fe 2Fe22OO33

How many grams of iron (III) oxide can be How many grams of iron (III) oxide can be produced with 17.2g Fe?produced with 17.2g Fe?

4Fe + 3O4Fe + 3O22 2Fe 2Fe22OO33

How many grams of iron will react with How many grams of iron will react with 5.25 liters of O5.25 liters of O22 (@STP)? (@STP)?

4Fe + 3O4Fe + 3O22 2Fe 2Fe22OO33

How many molecules of OHow many molecules of O22 are needed to are needed to

produce 3.92g Feproduce 3.92g Fe22OO33??

Density

Remember, a conversion from liters to moles is only valid for gases at STP.

Converting from/to liters (or mL) for liquids or solids involve using density as a conversion factor.

If you have 10.0mL of isopropyl If you have 10.0mL of isopropyl alcohol (Calcohol (C33HH77OH) and burn it, OH) and burn it,

how many liters COhow many liters CO22 gas are gas are

produced @STP? The reaction produced @STP? The reaction is combustion. is combustion.

D = 0.798g/mLD = 0.798g/mL

10.0mL (C10.0mL (C33HH77OH) OH)

D = 0.798g/MlD = 0.798g/Ml how many liters CO how many liters CO22

Find Mass using D=M/VFind Mass using D=M/V

Write the reaction2C2C33HH77OH + 9OOH + 9O22 6CO6CO22 + 8H + 8H2200

7.98g ? L7.98g ? L