IB Chemistry Topic R2.1.1 Chemical Equations and Stoichiometry Revision Notes (SL/HL)

IB Chemistry Topic R2.1.1 Chemical Equations and Stoichiometry Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Chemical Equations and Their Role in Representing Reactions

Analogy

Consider that you are baking a cake.
The recipe specifies exact amounts of flour, sugar, eggs, and butter to create the perfect dessert.
If you use too much or too little of any ingredient, the result might not turn out as expected.

In chemistry, a chemical equation serves as this "recipe" for a chemical reaction. It tells you the precise ratios of reactants (ingredients) and products (results) involved.

Representing Chemical Reactions with Equations

Definition

Chemical equation

A chemical equation is a symbolic representation of a chemical reaction. It shows the reactants (starting substances) on the left side, the products (substances formed) on the right, and an arrow indicating the direction of the reaction.

Example

$$C_2H_6 + O_2 \rightarrow CO_2 + H_2O$$

This equation represents the combustion of ethane ($C_2H_6$) in oxygen ($O_2$) to produce carbon dioxide ($CO_2$) and water ($H_2O$).
However, this equation is not yet complete: it must be balanced to adhere to the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.

Balancing Chemical Equations: Why and How?

When balancing a chemical equation, the goal is to ensure the number of atoms of each element is the same on both sides of the equation.
This reflects the fact that atoms are simply rearranged during a reaction, not created or destroyed.

Steps to Balance a Chemical Equation:

Write the unbalanced equation:
1. Start by listing the reactants and products.
2. For example, $C_2H_6 + O_2 \rightarrow CO_2 + H_2O$

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Tip

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Chemical Equations and Their Role in Representing Reactions

Analogy

Consider that you are baking a cake.
The recipe specifies exact amounts of flour, sugar, eggs, and butter to create the perfect dessert.
If you use too much or too little of any ingredient, the result might not turn out as expected.

In chemistry, a chemical equation serves as this "recipe" for a chemical reaction. It tells you the precise ratios of reactants (ingredients) and products (results) involved.

Representing Chemical Reactions with Equations

Definition

Chemical equation

Example

$$C_2H_6 + O_2 \rightarrow CO_2 + H_2O$$

This equation represents the combustion of ethane ($C_2H_6$) in oxygen ($O_2$) to produce carbon dioxide ($CO_2$) and water ($H_2O$).
However, this equation is not yet complete: it must be balanced to adhere to the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.

Balancing Chemical Equations: Why and How?

When balancing a chemical equation, the goal is to ensure the number of atoms of each element is the same on both sides of the equation.
This reflects the fact that atoms are simply rearranged during a reaction, not created or destroyed.

Steps to Balance a Chemical Equation:

Write the unbalanced equation:
1. Start by listing the reactants and products.
2. For example, $C_2H_6 + O_2 \rightarrow CO_2 + H_2O$

Definition

Paywall

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Note

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Excepteur sint occaecat cupidatat non proident

Tip

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Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

IB Chemistry R2.1.1 Chemical Equations and Stoichiometry Notes

Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

Chemical Equations and Their Role in Representing Reactions

Representing Chemical Reactions with Equations

Balancing Chemical Equations: Why and How?

Steps to Balance a Chemical Equation:

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Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Chemical Equations and Their Role in Representing Reactions

Representing Chemical Reactions with Equations

Balancing Chemical Equations: Why and How?

Steps to Balance a Chemical Equation:

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Duis aute irure dolor in reprehenderit

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