Chemical Equations

A Quick Review…

• Chemical symbol:A shorthand notation for an element’s name.

A shorthand notation for a compound or a molecule.

• Chemical formula:

A Quick Review…

• Chemical reaction:The process by which one or more substances undergo change to produce one or more different substances.

• Writing out a chemical reaction can take a long time and isn’t universal, so there exists a simpler way to represent a chemical reaction called a…

Chemical Equations

• Chemical equation:A shorthand notation of a chemical reaction using chemical formulas and symbols.

• Example:

C + O2 CO2

Parts of a Chemical Equation

C + O2 CO2

Reactants: the starting materials in a chemical reaction. (LEFT) - Written before the arrow.

Products: the substances formed in a reaction. (RIGHT) - Written after the arrow.

Parts of a Chemical Equation

C + O2 CO2

Plus sign: reads: ‘reacts with’.Carbon reacts with dioxide

Arrow: Reads ‘to produce’ or ‘to yield’

Carbon reacts with dioxide to yield Carbon dioxide.

Why We Counted Atoms

C + O2 CO2

The number of atoms we start with (reactants side) must equal the number of atoms we end up with (products side).

All equations must be balanced. The number of atoms of each element in a reactant must equal the number of the same elements in the product.

Reactants = Products

Why We Counted Atoms

C + O2

When counting atoms for each side, think of the yield sign as an equal sign.

C + O2 O2=• The number of Carbon in the reactants must equal the number of Carbon in the product.

• The number of Oxygen in the reactants must equal the number of Oxygen in the product.

C

O2C

Balancing the Equation

C + O2 O2C

• Divide the equation into a chart.

Balancing the Equation

C +

O

O2C

•Count the number of atoms of each element on the reactants side using symbols to represent the number of atoms.

C

O2

O

• Are all atoms counted for on the left side? If so, we can move to the right side of the arrow.

Balancing the Equation

C +

O

O2C

• Repeat the same process for the right side as you did with the left side.

C

O2

OOCO

Balancing the Equation

C +

O

O2C

• Start with Carbon and count each side.

C

O2

OOCO

1 1

• Do we have an equal amounts of Carbon?

Let’s move on to Oxygen

Balancing the Equation

C +

O

O2C

• Now Count the Oxygen on each side.

C

O2

OOCO

2

• Do we have an equal amounts of Oxygen?

We have a BALANCED equation.

2

Balancing the Equation

C + O2CO2

Balancing the Equation

C +

O2C

O 2

A Balanced Equation

C + O2CO2

Balancing Example

H2 + O2 OH2

Dihydrogen reacts with Dioxideto yield Dihydrogen monoxide.

Balancing Example

H2 + O2 OH2

HH

OO

•Count the number of atoms of each element on the reactants side using symbols to represent the number of atoms.

Balancing Example

H2 + O2 OH2

HH

OO

• Repeat the same process for the right side as you did with the left side.

HH

O

Balancing Example

H2 + O2 OH2

HH

OO

HH

O

• Start with Hydrogen and count each side.• Do we have an equal amounts of Hydrogen?

22

Balancing Example

H2 + O2 OH2

HH

OO

HH

O

• Now count Oxygen on each side.• Do we have equal amounts of Oxygen?

2 1

Balancing Example

H 2+ O 2

OH 2

• We cannot leave an equation unbalanced. What can be done to fix it?

Balancing Example

H2 + O2 OH2

HH

OO

HH

O

HH O

Balancing Example

• The equation is still unbalanced. What can be done to fix it?

H2 +O

2

OH2

Balancing Example

H2 + O2 OH2

HH

OO

HH

O

• Are Oxygen atoms equal on both sides?

HH O

• Are Hydrogen atoms equal on both sides?

Let’s try and fix Hydrogen.

HH

Balancing Example

H2 + O2 OH2

HH

OO

HH

O

• The number of boxes represents the coefficient.

HH O

• What is the coefficient in front of H2?

HH

• What is the coefficient in front of H2O?

2 21

A Balanced Equation

H2 + O2 OH222 1

Practice

H2 + Cl2 ClH

HH

ClCl

HClClH

211

Dihydrogen reacts with dichloride to yield Hydrogen monocholoride.

Practice

N2 + H2 H3N

NN

HH

NHHHNHHH

HH

HH

3 21

Dinitrogen reacts with dihydrideto yield Nitrogen trihydride.

Practice

Na + Cl2 F2NaCl+F

NaF ClCl

Na FClFNaClNaF

2 1 2 1

Sodium Fluoride reacts with Dichloride to yield Sodium Chloride and Difluoride