Chapter 10

Chemical Reactions

Section 10.1 Reactions & Equations

Chemical reaction—process by which the atoms of 1 or more substances are rearranged to form different substances

Evidence of chemical reactions: (fig 10.1) Temperature change—release energy in the

form of heat & light Color change Odor is detectable Gas bubbles Appearance of a solid (precipitate)

Section 10.1 Reactions & Equations

Reactants—starting substances Products—substances formed during

reaction An arrow () separates products from

reactants. You would read the arrow as “react to produce” or “yield.”

Section 10.1 Reactions & Equations

Physical states of matter are shown in parentheses. (s) = solid (l) = liquid (g) = gas (aq) = aqueous; water solution

Word Equation Iron(s) + chlorine(g) iron(III)

chloride(s)

Skeleton Equation—use chemical formulas rather than words Fe(s) + Cl2(g) FeCl3(s)

Ex. Solid carbon & solid sulfur(S8) react to form solid carbon disulfide.

Work practice problems 1-3.

Practice

1. hydrogen(g) + bromine(g) hydrobromic acid (aq)

2. carbon monoxide(g) + oxygen(g) carbon dioxide(g)

3. potassium chlorate(s) potassium chloride(s) + oxygen(g)

Word & skeleton equations lack important information. A true chemical equation must show that matter is conserved.

Balancing Chemical Equations Use coefficients—whole # written in front of a formula Do NOT use 1 as a coefficient in balancing. The coefficient represents the lowest whole number

ratio.1. write the skeleton equation.2. count the atoms of reactants & products one at a time.

(count individual elements in polyatomic ions)3. change the coefficient to make the number of atoms of

each element equal on both sides of the arrow **NEVER BALANCE BY CHANGING THE

SUBSCRIPTS** **SAVE OXYGEN & HYDROGEN FOR LAST**

Balancing equations

Example:N2(g) + H2(g) NH3(g)

Practice: Balancing equations

1. H2(g) + Br2(g) HBr(g)

2. CO(g) + O2(g) CO2(g)

3. KClO3(s) KCl(s) + O2(g)

4. Carbon & sulfur react to form carbon disulfide.

** Balance…

10.2 Classifying Chemical Reactions

1. SYNTHESIS reaction- two or more substances react to form a single product.

A + B AB

Na + Cl2 __________

Example: Synthesis Rxn

Mg + N2

Mg+2 N-3

Mg3N2

Practice: Synthesis Rxn

__________ CaO

Iron (III) + Oxygen __(formula)____________

10.2 Classifying Chemical Reactions

2. Combustion reaction- O2 combines with a substance often forming CO2 &/or H2O. (Similar to synthesis)

H2 + O2 H2O

___ + O2 CO2

Example: Combustion Rxn

CH4(g) + O2(g) CO2(g) + H2O(g)

Practice: Write a balanced equation & determine type of reaction

1. The solids aluminum and sulfur(S8) react to produce solid aluminum sulfide.

2. The gases nitrogen dioxide and oxygen react to produce dinitrogen pentoxide gas.

3. Ethane gas (C2H6) burns in air to produce carbon dioxide gas and water vapor.

10.2 Classifying Chemical Reactions

3. Decomposition reaction- a single compound breaks into 2 or more new compounds.

AB A + B Na3N (s) __ (s) + __ (g)

Decomposition of sugar

Example: Decomposition Rxn

___________ Hg (l) + O2 (g)

assume it is mercury (II)

Practice: Decomposition Rxn

1. Al2O3(s) ________+_______

2. Aqueous nickel(II) hydroxide decomposes to produce nickel(II) oxide & water.

3. Cu2S ___________

Classify the reaction Na + O2 Na2O

Synthesis CaO Ca + O2

Decomposition CH4 + O2 H2O + CO2

Combustion KClO3 KCl + O2

Decomposition O2 + C5H12 CO2 + H2O

Combustion Al + F2 AlF3

Classify the reaction

1. C6H14 + O2

2. Mg + N2

3. H2O2

4. Ag + S 5. Zn + O2

6. C12H22O11

4. Single Replacement reaction- an atom replace the atom in a compound.

A + BX AX + B

Cu(II) (s) + 2AgNO3 (aq)

________________

Activity Series:

-------------over there

Cu(II) (s) + 2AgNO3 (aq)

________________

Copper plating

Example: Single replacement

Fe(II) (s) + CuSO4(aq)

(Fe+2 + Cu+2 + SO4-2)

FeSO4(aq) + Cu

Practice 2-6

2. Ag(s) + AlPO4(aq) NR (no reaction)

3. Mg(s) + AlCl3(aq) MgCl2(aq) + Al(s)

4. K(s) + ZnCl2(aq) KCl(aq) + Zn(s)

5. Br2(l) + MgCl2(aq) NR

*6. F2(g) + CaCl2(aq) CaF2(aq) + Cl2(g)

5. Double-replacement reaction- Two compounds react to form 2 new compounds.

In this reaction water, a gas or a solid can be formed.

AX + BY AY + BX

Double replacement rxn

Example: Double-replacement Rxn

Ca(OH)2(aq) + 2HCl(aq) Ca+2 + OH-1 + H+1 + Cl-1

CaCl2(aq) + 2H2O(l)

Practice: Double Replacement Rxn

NaOH(aq) + CuCl2(aq) Na+1 + OH-1 + Cu+2 + Cl-1 NaCl(aq) + Cu(OH)2(s)

KCN(aq) + HBr(aq) K+1 + CN-1 + H+1 + Br-1

KBr + HCN

Practice:Give the balanced skeletal for the following.

1. Aqueous barium chloride and aqueous potassium carbonate react to produce solid barium carbonate and aqueous potassium chloride.

BaCl2(aq) + K2CO3(aq) BaCO3(s) + 2KCl(aq)

2. Aqueous lithium iodide and aqueous silver(I) nitrate react to produce solid silver(I) iodide and aqueous lithium nitrate.

LiI(aq) + AgNO3(aq) AgI (s) + LiNO3(aq)

Classify each rxn CH4 + O2 H2O + CO2

Combustion KClO3(s) KCl(s) + O2(g)

decomposition ZnCl2(aq) + K(s) KCl(aq) + Zn(s)

Single-replacement

BaCl2+ K2CO3 BaCO3+ 2KCl Double-replacement

CaCl2(aq) + F2(g) CaF2(aq) + Cl2(g) Single-replacement

Classify & Predict CuO Mg + O2 Ca + N2 C3H8 + O2 HCl + BaSO4 Fe + CuCl2 Cu3N + Zn **Classify each equation on “Balancing eq”

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