Writing and Balancing Chemical Equation

Is the process by

which a chemical

change takes place.

A change where a

new substance

is formed.

Is the shorthand way of

expressing chemical reaction

using numbers, symbols

and formula.

REACTANTS

The starting materials

These are the

substances that

changes when it is

combined with another

substance in a

chemical reaction

PRODUCTS

The new substance

The substances that

result of the chemical

reaction

COEFFICIENT SUBSCRIPT

is a number before

the symbol or formula

of a substance

is the number of

atoms of the element

found in the

substance

Symbols Meaning

+used to separate one reactant or

product from one another.

Can be read as “reacts with”

when used in reactant , read as

“and” when it is used in product.

used to separate the reactants

from the products

read as "yields" or "produces" in

an equation.

(s) indicates that the substance is in

the solid state.

Symbols Meaning

(l) indicates that the substance is in

the liquid state.

(g) indicates that the substance is in

the gas state.

(aq) indicates that the substance is

dissolved in water

comes from the term “aqueous”

indicates that there is heat

applied or needed to make the

reaction proceed.

Sodium + Water

Sodium Hydroxide + Hydrogen gas

EXAMPLE

:

𝑵𝒂(𝒔) +2 𝑯𝟐𝑶(𝒍) NaO𝑯(𝒔) + 𝑯𝟐(𝒈)

Reactants Symbol Products

Coefficient

Subscript

C(s) + O2(g) CO2(g) + energy

Mg(s) + Cl2(g) MgCl2(s)

TRY THIS:

the sum of the masses of the products is

always the same as the sum of the masses of

the reactants.

states that mass is neither created nor

destroyed in any ordinary chemical reaction.

1. Check for diatomic molecules.

-are molecules composed of only

two atoms, of either the same or different

chemical elements.

This includes 𝐻2, 𝑂2, 𝑁2, 𝐶𝑙2,

𝐵𝑟2, 𝐹2 and 𝐼2.

2. Check whether the chemical formulas of all

the reactants and products are correct. Check

the total number of atoms of each element on

each side of the equation.

3. A polyatomic ion appearing unchanged on

both sides of the equation is counted as a single

unit.

4. Balance the elements one at a time by using

coefficients. Must not attempt to the balance the

equation by changing the subscripts in the

chemical formula of a substance.

5. Check each atom or polyatomic ion to be

sure that the equation is balanced.

EXAMPLES

:

STEP 1:

Element Reactants Products

H 2 2 Equal

O 2 1 Not

equal

STEP 2:

Element Reactants Products

N 2 1 Not

equal

H 2 3 Not

equal

Chemical Equation during Photosynthesis:

CO2(g) + H2𝑶(𝒍) → C6H12O6(s) + O2(g)

Chemical Equation when cooking in the

gas stove:

CH4(g) + O2(g) → CO2(g) + H2 𝑶(𝒍)

Chemical Equation in the Formation of Rust:

Fe(s) + O2(g) → Fe2O3(s)

1. 6 CO2(g) +6 H2𝑶(𝒍) → C6H12O6(s) + 6 O2(g)

2. CH4(g) + 3 O2(g) → CO2(g) +2 H2 𝑶(𝒍)

3. 4 Fe(s) + 3 O2(g) → 2 Fe2O3(s)

DIRECTIONS: On a one whole sheet of paper, Answer the following questions.

1. What are the types of chemical reactions?

2. Give at least 3 examples on each type.

Davis, Raymond E. et.al.(2010). Modern Chemistry. (USA: Holl, Rinehart, Winston).

de Borja, Rebecca S.(2011).Chemistry. (Philippines: Books Atbp. Publishing Corp.)

Hill, John W. (2010). Chemistry for Changing Times. (Singapore: Prentice Hall Companies).