chapter 11 chemical reactions chemical equation describes chemical reaction. describes chemical...

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Chapter 11 Chemical Reactions

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Page 1: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Chapter 11

Chemical Reactions

Page 2: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Chemical Equation

Describes chemical reaction. Chemical equation: reactants yield products

Reactants Products

Much easier to write symbols and formulas instead of words

Page 3: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Examples Solid Iron reacts with oxygen gas to form the solid

IronIIIoxide. iron(s) + oxygen(g) ironIIIoxide(s) Fe(s) + O2(g) Fe2O3(s)

Carbon tetrahydride gas BURNS to form carbon dioxide gas and water vapor.

Carbon tetrahydride(g) + oxygen(g) carbon dioxide(↑) + water(↑)

CH4(g) + O2(g) CO2(↑) + H2O(↑) Skeleton Equation: chemical equation that tells you what the

reactants and products are but NOT how much of each you have. First step in writing a chemical equation.

Page 4: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Symbols Used (s) solid (l) liquid (g) gas (↑) gas as a product (aq) aqueous (in water solution) () ppt (precipitate) solid product from 2

aqueous reactants D means with heat Pt means with Platinum catalyst: speeds up a

reaction without being used. reversible reaction

Page 5: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Balancing Chemical Equations

Balanced equations have: the same # of atoms of each element on

BOTH sides of the equation.

Law of Conservation of Mass – atoms can neither be created nor destroyed, simply rearranged.

Page 6: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Rules for Balancing Equations

Get the correct formulas for reactants and products.

(USE ION CHART AND DON”T FORGET DIATOMIC ELEMENTS!)

Write reactants on left, products on right. Use plus signs to separate compounds and yield sign to separate the reactants from products.

Page 7: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Rules Continued Count the # of atoms of each element in

reactants and products. (Polyatomic atoms on both sides count as one.)

Balance # of each element using coefficients.

Coefficient – small whole # in front of a formula.

NEVER CHANGE FORMULA SUBSCRIPTS

Page 8: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Rules for Balancing Equations

Balance elements appearing 3 or more places LAST.

Check each element to make sure equation is balanced.

Make sure all coefficients are in the lowest whole number ratio.

Do not change subscripts!!!

Page 9: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Diatomic Molecules

Diatomic Molecules- a molecule made up two atoms of the same element. They are only

diatomic when they are alone.

-There are 7 naturally occurring diatomic molecules.

H O N Cl Br I F

Page 10: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Balancing Examples

___ C(s) + ___ O2(g) ___ CO2 (g)

___ C(s) + ___ O2(g) ___ CO (g)

___ AgNO3(aq) + ___Cu(s) ___ Cu(NO3)2(aq) + ___ Ag(s)

___ Al(s) + ___ O3(g) ___ Al2O3(s)

*___ C2H6(g) + ___ O2(g) ___ CO2(g) + ___ H2O(g)

*___ H3PO3 ___ H3PO4 + PH3

Page 11: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

5 Types of Chemical Reactions

Combination Reaction – elements combine to form a compound.

A + B AB element + element compound Ex. Sodium + chlorine sodium chloride ___Na(s) + ___ Cl2(g) ___ NaCl(s)2 2

Page 12: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

5 Types of Reactions

Decomposition Reaction – compound

breaks down into its element. AB A + B compound element + element Ex: MercuryII oxide mercury + oxygen ___ HgO ___Hg + ___O22 2

Page 13: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

5 Types of Reactions - 3

Single Replacement Reaction – one element replaces another element in a compound.

AB + C A + CBor

AB + D AD + B

+ - + + + -

+ - - + - -

Page 14: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Examples of Single Replacement Reactions

• Must use Activity Series to see if reaction works

• Zinc + sulfuric acid zinc sulfate + hydorgen

• Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(↑)

• Periodic table is activity series for halogens

• Sodium bromide + chlorine sodium chloride + bromine

• ___NaBr(s) + ___Cl2(g) ___NaCl(s) + ___Br2(↑)22

Page 15: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

5 Types of Reactions

Double Replacement Reaction – two compounds react and exchange positive ions to form two new compounds.

AB + CD AD + CB Barium Chloride(aq) + potassium carbonate(aq)

barium carbonate() + potassium chloride(aq)

BaCl2(aq) + K2CO3(aq) BaCO3() + ___ KCl(aq)

+ - + - + - + -

2

Page 16: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

5 Types of Reactions Combustion Reaction – oxygen reacts with a

compound composed of C and H.

CxHy + O2 CO2 + H20

Also called Burning (exothermic)

The products are always CO2 and H2O.

Page 17: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Examples of Combustion Reactions

1. C6H6 + O2 CO2 + H2O

2. CH3OH + O2 CO2 + H2O

367½

21½

CH3OH + O2 CO2 + H2O2 3 2 4

C6H6 + O2 CO2 + H2O 2 15 12 6

Page 18: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Special Decomposition Reactions:

Decomposition of a Carbonate: Metal carbonate metal oxide + carbon dioxide

XCO3 XO + CO2

ex. Na2CO3 Na2O + CO2

Page 19: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Special Decomposition Reactions:

Decomposition of a Hydroxide: Metal hydroxide metal oxide + water

XOH XO + H2O

ex. 2NaOH Na2O + H2O

Page 20: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Special Decomposition Reactions:

Decomposition of a Chlorate: (ClO3) Metal chlorate metal chloride + oxygen

XClO3 XCl + O2

ex. ___NaClO3 ___NaCl + ___O22 3

Page 21: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

Special Decomposition Reactions: 4

Special single Replacement Reaction:»Group IA or IIA metal and H2O

X + HOH XOH + H2

ex. 2Na + 2HOH 2NaOH + H2

Page 22: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products

How to ID types of reactions.Combination Reactions – given 2 items that form 1

new compound.Decomposition Reactions – given a single

compound that breaks into parts.Single Replacement – given a single element plus a

single compound, forms a new compound a a different element.

Double Replacement – given two compounds (+’s change places).

Combustion Reaction – given CH compound with Oxygen, always forms water and carbon dioxide.

Page 23: Chapter 11 Chemical Reactions Chemical Equation Describes chemical reaction. Describes chemical reaction. Chemical equation: reactants yield products