Balancing Chemical Equations

Term 3 Lesson 8

BALANCING
CHEMICAL
EQUATIONS

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• Combination /Synthesis Reaction

RECALL

TYPES OF CHEMICAL REACTIONS

• Decomposition Reaction

• Single Replacement Reaction

• Double Displacement Reaction

• Combustion Reaction

Match

LET'S REACT!

Match the following chemical equations to the type of chemical reactions.

combination / synthesis

decomposition

single replacement

complete combustion

double displacement

• combination / synthesis

• decomposition

• single replacement

• complete combustion

• double displacement

RECALL

Chemical reactions follow the Law of Conservation of Mass.

This states that mass is neither created nor destroyed but is conserved during a chemical reaction.

RECALL

Law of Conservation of Mass

RECALL

Law of Conservation of Mass

The overall mass of the reactants before the reaction must be equal to the overall mass of the products after the reaction.

The number of atoms of the elements in the reactants must be equal to the number of atoms of the elements in the products.

RECALL

Law of Conservation of Mass

Ag_(s) + S_(s) → Ag₂S_(s)

ANALYZE THE CHEMICAL EQUATION

Ag_(s) + S_(s) → Ag₂S_(s)

ANALYZE THE CHEMICAL EQUATION

How many atoms of silver (Ag) are on the reactants side?

Ag_(s) + S_(s) → Ag₂S_(s)

ANALYZE THE CHEMICAL EQUATION

How many atoms of silver (Ag) are on the product side?

Ag_(s) + S_(s) → Ag₂S_(s)

ANALYZE THE CHEMICAL EQUATION

How many atoms of silver (Ag) are on the reactants side? 1 atom

How many atoms of silver (Ag) are on the product side? 2 atoms

Does this chemical equation follow the Law of Conservation of Mass?

Ag(s) + S(s) → Ag2S(s)

ANALYZE THE CHEMICAL EQUATION

Since the number of atoms of the elements in the reactants is not equal to

the number of atoms of the elements in the product, this chemical equation is

DOES NOT FOLLOW the Law of Conservation of Mass.

Ag_(s) + S_(s) → Ag₂S_(s)

ANALYZE THE CHEMICAL EQUATION

If a chemical equation does not follow the Law of Conservation of Mass, then the chemical equation is NOT BALANCED.

A chemical equation must follow the Law of Conservation of Mass.

A balanced chemical equation is an equation wherein the number of each type of atom is equal on the reactant and the product side of the equation.

WHY DO WE

BALANCE
CHEMICAL

EQUATIONS?

WHY DO WE BALANCE A CHEMICAL EQUATION?

We balance a chemical equation so that the equation will conform to

the Law of Conservation of Mass.

It allows us to properly and correctly determine the mass of the

reactants and the products in a reaction.

HOW DO WE
BALANCE A
CHEMICAL
EQUATION?

HOW DO WE BALANCE A CHEMICAL EQUATION?

Step 1. Write the skeleton equation.

Step 2. Count the number of atoms of the elements in the reactants.

Step 3. Count the number of atoms of the elements in the products.

Step 4. Check if the number of atoms of the elements are the same in both
sides of the chemical equation.

Step 5. Add coefficients before each compound to make the number of atoms
of each element in both sides of the chemical equation the same.

SAMPLE PROBLEM #1:

Write the balanced chemical equation when solid silver (Ag) metal combines with solid sulfur (S) powder to form silver sulfide (Ag2S).

SAMPLE PROBLEM #1:

Write the balanced chemical equation when solid silver (Ag) metal combines with solid sulfur (S) powder to form silver sulfide (Ag2S).

Skeleton Equation: Ag(s) + S(s) → Ag2S(s)

SAMPLE PROBLEM #1:

Write the balanced chemical equation when solid silver (Ag) metal combines with
solid sulfur (S) powder to form silver sulfide (Ag2S)

Skeleton Equation: Ag(s) + S(s) → Ag2S(s)

Is the skeleton equation balanced?

Element

No. of Atoms in the Reactant

No. of Atoms in the Product

Silver (Ag)

Sulfur (S)

SAMPLE PROBLEM #1:

Write the balanced chemical equation when solid silver (Ag) metal combines with
solid sulfur (S) powder to form silver sulfide (Ag2S).

Skeleton Equation: Ag(s) + S(s) → Ag2S(s)

Is the skeleton equation balanced?

Element

No. of Atoms in the Reactant

No. of Atoms in the Product

Silver (Ag)

1

Sulfur (S)

SAMPLE PROBLEM #1:

Write the balanced chemical equation when solid silver (Ag) metal combines with
solid sulfur (S) powder to form silver sulfide (Ag2S).

Skeleton Equation: Ag(s) + S(s) → Ag2S(s)

Is the skeleton equation balanced?

Element

No. of Atoms in the Reactant

No. of Atoms in the Product

Silver (Ag)

1

2

Sulfur (S)

SAMPLE PROBLEM #1:

Write the balanced chemical equation when solid silver (Ag) metal combines with
solid sulfur (S) powder to form silver sulfide (Ag2S).

Skeleton Equation: Ag(s) + S(s) → Ag2S(s)

Is the skeleton equation balanced?

Element

No. of Atoms in the Reactant

No. of Atoms in the Product

Silver (Ag)

1

2

Sulfur (S)

1

SAMPLE PROBLEM #1:

Write the balanced chemical equation when solid silver (Ag) metal combines with
solid sulfur (S) powder to form silver sulfide (Ag2S).

Skeleton Equation: Ag(s) + S(s) → Ag2S(s)

Is the skeleton equation balanced?

Element

No. of Atoms in the Reactant

No. of Atoms in the Product

Silver (Ag)

1

2

Sulfur (S)

1

1

SAMPLE PROBLEM #1

Write the balanced chemical equation when solid silver (Ag) metal combines with
solid sulfur (S) powder to form silver sulfide (Ag₂S).

Skeleton Equation: Ag(s) + S(s) → Ag₂S(s)

What coefficient should you place to make the chemical equation balanced?

___Ag_(s) + ___ S_(s) → ___Ag₂S_(s)

REMEMBER!

We can only include coefficients but we cannot change the subscripts of the
compounds or elements in a reaction.

Ag(s) + S(s) → Ag2S(s)

Off Limits!

SAMPLE PROBLEM #1

What coefficient should you place to make the chemical equation balanced?

__Ag_(s) +__ S_(s) → __ Ag₂S_(s)

SAMPLE PROBLEM #2:

Write the balanced chemical equation when zinc (Zn) reacts with hydrochloric
acid (HCl) to produce zinc chloride (ZnCl₂) and hydrogen (H₂) gas.

Skeleton Equation:

SAMPLE PROBLEM #2:

Write the balanced chemical equation when zinc (Zn) reacts with hydrochloric
acid (HCl) to produce zinc chloride (ZnCl₂) and hydrogen (H₂) gas.

Skeleton Equation: Zn + HCl → ZnCl₂ + H₂

Draw

PRACTICE!

Write the balanced chemical equation when mercury (II) oxide (HgO) decomposes to mercury (Hg) and oxygen gas (O₂).

PRACTICE!

Write the balanced chemical equation when mercury (II) oxide (HgO)
decomposes to mercury (Hg) and oxygen gas (O₂).

Skeleton Equation: HgO → Hg + O₂

Self-Assessment

Answer the following as truthfully as possible to check if you have achieved the Learning Targets of our lesson.

Poll

I can apply the law of conservation of mass in balancing equations.

• CLEAR

  (I understand and can do this by myself.)

• CLOUDY

  (I understand and can do this but in some parts will need to clarify a few things.)

• STORMY

  (I do not understand at all nor am I able to do any of the required task. I am very confused.)

Poll

I can create a balanced chemical equation.

• CLEAR

  (I understand and can do this by myself.)

• CLOUDY

  (I understand and can do this but in some parts will need to clarify a few things.)

• STORMY

  (I do not understand at all nor am I able to do any of the required task. I am very confused.)

ESSENTIAL QUESTIONS

How do we balance chemical equations?

Why do we balance chemical equations?

We balance by inspecting if the number of atoms in the reactants are equal to

the number of atoms in the product.

We include coefficients to the reactants and products until the whole equation is

balanced.

Asynchronous Activity

• Answer the Graded Worksheet on Writing and Balancing Chemical Equations in Canvas.

Reminder for Next Meeting

• Bring lab gown, goggles, gloves and lab kit for our experiment.

VALUING

Everyday, students are faced with various subjects to study together with other extra-curricular activities.

VALUING

Just like chemical equations that need to be balanced, how can students balance personal life and studies?

VALUING

VALUING

VALUING

How do we practice life-study balance?

• Plan your schedule.

• Make a weekly to-do list.

• Prioritize your tasks.

• Break large tasks into their smaller components.

• Set goals and deadlines for projects.

• Avoid perfectionism.

• Honestly assess the amount of time you waste.