Chapter 10

Chemical Reactions

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Homework for Chap 10Homework for Chap 10

Read p 273 – 286; 288 - 293

Applying the Concepts # 1 – 37,

39 – 42, 44 – 47, 49 - 53

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Molecular formula shows the actual number of atoms of each element in the smallest unit of a substance

Empirical formula shows the simplest whole-number ratio of the atoms in a substance

H2OH2O

molecular empirical

C6H12O6 CH2O

O3 O

N2H4 NH2

Chemical FormulasChemical Formulas

Fig. 10.2 Several ways to express common molecules

3 ways of representing the reaction of H2 with O2 to form H2O

Chemical reaction ≡ process in which one or more substances is changed into one or more new substances

Chemical equation ≡ use of chemical symbols to show what happens during a chemical reaction

reactants products

Fig. 10.4 The Combustion of Charcoal

C + O2 → CO2

“Carbon reacts with oxygen to yield carbon dioxide”

Fig. 10.5 The meaning of subscripts and coefficients

Fig. 10.6 Illustration of the Law of Conservation of Mass

Fig. 10.8 Hydrocarbons and Carbohydrates

C8H18

C3H8

C12H22O11

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Types of Chemical ReactionsTypes of Chemical Reactions

1) Oxidation-Reduction (Redox)

2) Combination

3) Decomposition

4) Replacement

5) Ion Exchange

(electron transfer reactions)

2 Mg (s) + O2 (g) 2 MgO (s)

Mg is the reducing agent (supplieselectrons and is oxidized)

O2 is the oxidizing agent (takes electronsand is reduced)

Oxidation – an atom loses electrons

Reduction – an atom gains electrons

Mg2+O2-

Fig. 10.9 Example of an oxidizing agent (“chlorine”)

Others:

1) Bleach

2) Hydrogen

peroxide

3) Oxygen

4) Ultraviolet

light

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Types of Chemical ReactionsTypes of Chemical Reactions

1) Oxidation-Reduction (Redox)

2) Combination

3) Decomposition

4) Replacement

5) Ion Exchange

Fig 10.10 Iron combines with oxygen to form rust (iron oxide)

4 Fe (4 Fe (ss) + 3 O) + 3 O22 ( (gg) 2 Fe) 2 Fe22OO33 ( (ss))

Hydrogen combines with oxygento form water (dihydrogen monoxide)

          

      

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Types of Chemical ReactionsTypes of Chemical Reactions

1) Oxidation-Reduction (Redox)

2) Combination

3) Decomposition

4) Replacement

5) Ion Exchange

FIG. 10.11 DECOMPOSITION OF MERCURY OXIDE

2 HgO (s) → 2 Hg (l) + O2 (g)heat

Decomposition of Hydrogen PeroxideDecomposition of Hydrogen Peroxide

2 H2 H22OO22 (l)(l) → 2 H→ 2 H22O O (l)(l) + O + O22 (g)(g)

(Demo)(Demo)

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Types of Chemical ReactionsTypes of Chemical Reactions

1)1) Oxidation-Reduction (Redox)Oxidation-Reduction (Redox)

2)2) CombinationCombination

3)3) DecompositionDecomposition

4)4) ReplacementReplacement

5)5) Ion ExchangeIon Exchange

Fig. 10.13 Replacement reaction between aluminum metal and the blue copper chloride solution

2 Al (s) 3 CuCl2 (aq) → 2 AlCl3 (aq) + 3 Cu (s)

CuClCuCl22

CuCuAlAl

AlClAlCl33

• Replacement reactions take place whenReplacement reactions take place whena more active metal gives up electronsa more active metal gives up electronsto a less active metal.to a less active metal.

• How do we know if a replacement reactionHow do we know if a replacement reactionwill take place or not occur?will take place or not occur?

• Refer to Refer to the activity seriesthe activity series for common metals for common metals

• Fig 10.12, p 264Fig 10.12, p 264

Fig. 10.12 The activity series for common metals

Fig. 10.12 The activity series for common metals

2 Na + 2H2 Na + 2H22O O 2NaOH + H2NaOH + H2 2 ↑↑

Zn + 2HCl ZnClZn + 2HCl ZnCl22 + H + H22 ↑ ↑

Cu + HCl no reactionCu + HCl no reaction