Unit: Chemical ReactionsDiatomic elements, Writing formula

equations from word equations

Day 1 - Notes

Day 1 - Notes

After today you will be able to…

• Name the diatomic elements• Write formula equations given the

word equation for a chemical reaction

• A chemical equation represents a chemical reaction.

Reactants Products“Yield”

• Reactants and products are separated from each other with a plus (+) sign.

Common forms of chemical reactions…

A + B CA B + C

A + B C + D

Chemical equations can be written as word equations or formula equations.

Formula equations can be balanced or unbalanced.

Word Equation: Iron + Oxygen Iron (III)

Oxide

Formula Equation: 4Fe(s) + 3O2(g) 2Fe2O3(s)

Balanced!

Symbols in Chemical Equations

Symbol Meaning(s) Solid(l) Liquid(g) Gas(aq) Aqueous (dissolved in H2O)

Reversible reaction

or Heat is added

Catalyst is added (A substance

that speeds up a reaction.)

To change word equations into

formula equations follow the flow

chart…

•Just write the symbolExample: “Sodium”=Na

•Br2 I2 N2 Cl2 H2 O2 F2

•Have the subscript “2”Examples: “Bromine”=Br2

“Hydrogen” = H2

•Balance charges!!!Example: “calcium chloride”

Ca+2 Cl-1

Cl-1

•Prefixes for subscriptsExamples:“dinitrogen tetraoxide”CaCl2 N2O4

(M +nM)

(nM +nM)

Let’s try some examples!

Examples: Convert into formula equations…

1. sodium chloride + fluorine sodium fluoride + chlorine

2. aluminum + sulfur aluminum sulfide

Helpful tip: Keep all substances and + signs in line with each other!

Na+1 Cl-1 Na+1 F-1

NaCl NaFF2 Cl2++

Al + S

Al+3 S-2

Al2S3

3. zinc + magnesium zinc + magnesium

ZnS

Zn+2 S-2 Mg+2 (AsO4)-

3

+ Mg3(AsO4

)2

Zn+2 (AsO4)-3

Zn3(AsO4

)2

Mg+2 S-2

MgS+

sulfide arsenate arsenate sulfide

Do now: Complete “Exit Ticket”

Then: Begin WS 1 (Homework)