Chapter 9 - Sections 1& 2

Suggested Reading:

Pages 299 - 305

Chapter 9 - Sections 1& 2

Suggested Reading:

Pages 299 - 305

StoichiometryStoichiometry

The study of the quantitative, or measurable, relationships that exist in chemical formulas and chemical reactions.

StoichiometryStoichiometry

2 H2 H22 + O + O22 2 H 2 H22OO

Interpreting Balanced Chemical EquationsInterpreting Balanced Chemical Equations

• Based on the mole ratio

Mole RatioMole RatioMole RatioMole Ratio

• indicated by coefficients in a balanced equation

Molar ratio of H2 to H2O is 2:2

(Simplify 1:1)

Molar ratio of O2 to H2O is 1:2

2 H2 H22 + O + O22 2 H 2 H22OO

2 moles of hydrogen react with

1 mole of oxygen to produce 2

moles of water.

2 H2 H22 + O + O22 2 H 2 H22OO

In terms of molesIn terms of moles

4 grams of hydrogen react with

32 grams of oxygen to produce

36 grams of water.

2 H2 H22 + O + O22 2 H 2 H22OO

In terms of massIn terms of mass

Law of Conservation of Matter & Law of Conservation of Matter & MassMassLaw of Conservation of Matter & Law of Conservation of Matter & MassMass

2 moles H2 react with 1 mole of

O2 to form 2 moles of H2O.

2 H2 H22 + O + O22 2 H 2 H22OO

HH22 OO22 HH22OO2 mol 1 mol 2 mol2 g

1 mol

32 g

1 mol

18 g

1 mol

4 g 32 g 36 g++ ==

VERIFIED!VERIFIED!VERIFIED!VERIFIED!

2 hydrogen molecules react with 1 oxygen

molecule to produce 2 water molecules.

• Notice that the number of molecules is

NOT the same on each side of the arrow.

2 H2 H22 + O + O22 2 H 2 H22OO

In terms of moleculesIn terms of molecules

4 atoms of hydrogen react with 2

atoms of oxygen to produce 2

water molecules, which are 4

atoms of hydrogen and 2 atoms

of oxygen.

2 H2 H22 + O + O22 2 H 2 H22OO

In terms of atomsIn terms of atoms

44.8 L of hydrogen gas react with 22.4 L

of oxygen gas to produce 44.8 L of water

vapor.

• Notice that the number of liters of gas is

NOT the same on each side of the arrow.

2 H2 H22 + O + O22 2 H 2 H22OO

In terms of volumes @ STPIn terms of volumes @ STP

Lead will react Lead will react with hydrochloric with hydrochloric acid to produce acid to produce lead (II) chloride lead (II) chloride and hydrogen. and hydrogen. How many moles How many moles of hydrochloric of hydrochloric acid are needed acid are needed to completely to completely react with 0.36 react with 0.36 moles of lead?moles of lead?

Practice Problem #1Practice Problem #1

Oh, no … Oh, no … where do I where do I start?start?

Lead will react with hydrochloric acid Lead will react with hydrochloric acid to produce lead chloride and to produce lead chloride and hydrogen. hydrogen.

Write an equation and balance it.Write an equation and balance it.

Pb + HCl Pb + HCl PbCl PbCl22 + H + H2222

How many moles of How many moles of hydrochloric acid hydrochloric acid are needed to completely react with are needed to completely react with 0.36 moles of 0.36 moles of leadlead??

Determine Mole RatioDetermine Mole Ratio

Pb + HCl Pb + HCl PbCl PbCl22 + H + H2222

hydrochloric hydrochloric acidacid

leadlead

Coefficient = 1Coefficient = 1Coefficient = 2Coefficient = 2

““wanted”wanted”““given”given”

How many moles of hydrochloric acid How many moles of hydrochloric acid are needed to completely react with are needed to completely react with 0.36 moles of0.36 moles of leadlead??

Set up mole ratio “wanted” to “given”Set up mole ratio “wanted” to “given”

PbPb + + HClHCl PbCl PbCl22 + H + H2222

0.36 moles 0.36 moles PbPb

2 HCl 2 HCl = .72 moles HCl= .72 moles HCl1 Pb1 Pb

Umm … It would Umm … It would require 0.72 moles require 0.72 moles of hydrochloric of hydrochloric acid. Is that right?acid. Is that right?

That’s Correct!That’s Correct!

Hem, hem –Hem, hem –you have 9 more you have 9 more problems … problems … ready, go.ready, go.