Chemical reactions I

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CHEMICAL REACTIONS

Reactants: Zn + I2

Product: Zn I2

Chemistry I – Chapter 11a Chemistry I Honors – Chapter 7 ICP – Chapter 21a

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Chemical Equations

Their Job: Depict the kind of reactants and products and their relative amounts in a reaction.

4 Al (s) + 3 O2 (g) ---> 2 Al2O3 (s)

The numbers in the front are called

stoichiometric

The letters (s), (g), and (l) are the physical states of compounds.

Slide 3

Chemical reactions occur when bonds between the outermost parts of atoms are formed or broken

Chemical reactions involve changes in matter, the making of new materials with new properties, and energy changes.

Symbols represent elements, formulas describe compounds, chemical equations describe a chemical reaction

Introduction

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Chemical equations show the conversion of reactants (the molecules shown on the left of the arrow) into products (the molecules shown on the right of the arrow).

A + sign separates molecules on the same side

The arrow is read as “yields”

Example

C + O2  CO2

This reads “carbon plus oxygen react to yield carbon dioxide”

Parts of a Reaction Equation

Slide 5

The charcoal used in a grill is basically carbon. The carbon reacts with oxygen to yield carbon dioxide. The chemical equation for this reaction, C + O2  CO2, contains the same information as the English sentence but has quantitative meaning as well.

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Because of the principle of the conservation of matter,

an equation must be balanced.

It must have the same number of atoms of the same kind on both sides.

Chemical Equations

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Solid _

Liquid (l)

Gas _

Aqueous solution (aq)

Catalyst H2SO4

Escaping gas ()

Change of temperature ()

Symbols Used in Equations

Slide 8

Balancing Equations

When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction, but you may not change the subscripts.