Writing & BalancingSimple Chemical Equations

CHEMICAL REACTION It is a process in which molecules interact to form new

substances.

Cookies

flourbutter

salt sugar

eggs

In a chemical reaction, the reacting substances (initial substances) are called reactants while the substances formed are called products.

Process Of Baking Cookies

WRITING CHEMICAL EQUATIONS

CHEMICAL EQUATION Is a symbolic representation of a chemical reaction.

Reactant A + Reactant B → Product

Symbol Purpose

+ Separates more than one reactant or product

Separates reactants from products. Indicates direction of reaction

(s) Identifies a solid state

(aq) Identifies that something is dissolved in water

(l) Identifies liquid state

(g) Identifies gaseous state

“carbon plus oxygen react to produce carbon dioxide” Example: C + O2 → CO2

STEPS FOR WRITING EQUATIONS

1. Identify the reactants and the products.

2. Write formulas for everything.3. Place the reactants on the left..4. Place the products on the right.

5. Place an arrow between them.

Simple Covalent Formulas

Water H2O

Carbon Dioxide CO2

Ammonia NH3

Hydrogen H2

Oxygen O2

Nitrogen N2

Sulfur Dioxide SO2

Methane CH4

Simple Ionic Formulas

Sodium Chloride NaCl

Calcium Chloride CaCl2

Magnesium Oxide MgO

Hydrochloric Acid HCl

Sulfuric Acid or Sulphuric Acid

H2SO4

Nitric Acid HNO3

Sodium Hydroxide NaOH

Potassium Hydroxide KOH

Calcium Hydroxide Ca(OH)2

Calcium Carbonate CaCO3

Aluminum Oxide Al2O3

Iron Oxide Fe2O3

EXAMPLES

In a precipitation reaction, sodium hydroxide solution is mixed with iron(II) chloride solution. Sodium Chloride solution and insoluble iron(II) hydroxide are produced.

Nitrogen and hydrogen react with each other to form ammonia.

Sodium reacts with water to form sodium hydroxide and hydrogen gas.

Dinitrogen tetrahydride reacts with oxygen to produce nitrogen and water.

BALANCING CHEMICAL EQUATIONS

Law of Conservation of Mass

In a chemistry, rxn, matter is neither created nor destroyed.

“If an equation obeys the Law of Conservation, it is balanced.

“

In other words, the number and type of atoms going INTO a rxn must be the same as the number and type of atoms coming OUT.

Subscripts and Coefficients

Subscript - shows how many atoms of an element are in a molecule.

Ex: H2O2 atoms of hydrogen (H)1 atom of oxygen (O)

Coefficient - shows how many molecules there are of a particular chemical.

Ex: 3 H2OMeans there are 3 water molecules.

Rules for Balancing Chemical Equation

• Matter cannot be created or destroyed.• Subscripts cannot be added, removed, or

changed.• Coefficients can only be change.• Coefficients can only go in front of chem.

formulas...NEVER in the middle of a formula.

Rules for Balancing Chemical Equation

• Try balancing big formulas first; save free elements for last.• If the same polyatomic ion appears on both sides of the

equation, it’s usually okay to treat it as one unit.• If the element to be balanced appears in only one substance on

one side of the equation and in another substance on the other side, get the least common multiple(LCM) of the numbers of atoms of this element. The LCM is also the number of atoms at which the element balances.

• There is no one particular way to balance equations. Some equations are harder to balance than others and might require some creativity to solve.

EXAMPLES1. Al + O2 → Al2O3

2. KCl03 → KCl + O2

3. Mg + AgNO3 → Mg(NO3)2 + Ag

4. (NH4)2 SO4 + Fe (SO3)3 → Fe2 (SO4)3 + NH4NO3

5. C3H7OH + O2 → CO2+ H2O

Aluminum + Oxygen → Aluminum Oxide

Potassium Chlorate → Potassium Chloride + Oxygen

Magnesium + Silver nitrate → Magnesium Nitrate + Silver

Ammonium sulfate + Iron(III) Sulfite → Iron(III) Sulfate + Ammonium Nitrate

Propanol + Oxygen →Carbon Dioxide + Water