Notes 6-2

Chemical Reactions

Chemical Formulas• The formula of a

compound identifies the elements in the compound and the ratios in which their atoms are present.

What Are Chemical Equations?

• Chemical equations use chemical formulas and other symbols instead of words to summarize a reaction.

Law of Conservation of Matter

• Matter is neither created nor destroyed

• *It is simply rearranged!

Conservation of Matter• The law of conservation of matter states that

in a chemical reaction, the total mass of the reactants must equal the total mass of the products.

Balancing Chemical Equations

• To describe a reaction accurately, a chemical equation must show the same number of each type of atom on both sides of the equation.

Examples from your lab:

• Acid + Base Water + Salt

• HCl + NaOH H2O + NaCl

• HCl + KOH H2O + KCl

Let’s try some!

____ AlBr3 + ____ K ____ KBr + ____ Al

Count the atoms:1 Aluminum atom 1 Potassium atom 1 Potassium atom 1 Aluminum atom3 Bromine atoms 1 Bromine atom

Is it balanced?No!

Add coefficients to balance atoms:

3 3

1 Aluminum atom 3 Potassium atoms 3 Potassium atoms 1 Aluminum atom3 Bromine atoms 3 Bromine atoms

Is it balanced?YES!

Let’s try some!

____ FeO + ____ PdF2 ____ FeF2 + ____ PdO

Count the atoms:1 Iron 1 Palladium 1 Iron 1 Palladium1 Oxygen 2 Flourine 2 Flourine 1 Oxygen

Is it balanced?YES!

Do we need to add coefficients?NO!

Let’s try some!

____ P4 + ____ Br2 ____ PBr3

Count the atoms:4 Phosphorus 2 Bromines 1 Phosphorus

3 Bromines

Is it balanced?No!

Add coefficients to balance atoms:

4 6

4 Phosphorus 12 Bromines 4 Phosphorus 12 Bromines

Is it balanced?YES!

Let’s try a harder one!

____ CoBr3 + ____ CaSO4 ____ CaBr2 + ____ Co2(SO4)3

Count the atoms:1 Co 1 Ca 1 Ca 2 Co3 Br 1 S 2 Br 3 S

4 O 12 O

Is it balanced?No!

Add coefficients to balance atoms:

3 3

2 Co 3 Ca 3 Ca 2 Co6 Br 3 S 6 Br 3 S

12 O 12 O

Is it balanced? YES!

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