Balancing Chemical Equations

Study Notes

Why balance equations?: To ensure that the number of atoms of each element is the same on both the reactant and product sides, conserving mass and satisfying the Law of Conservation of Mass.
Steps to balance an equation:
1. Write the unbalanced equation with the reactants on the left and products on the right.
2. Count the number of atoms of each element on both sides.
3. Identify the elements that are not balanced.
4. Add coefficients (numbers in front of formulas) to balance the equation, starting with the elements that appear most frequently.
5. Check the equation to ensure it is balanced.

Synthesis (Combination) Reactions: Two or more substances combine to form a new compound.
- General equation: A + B → AB
- Example: 2H2 + O2 → 2H2O
Decomposition Reactions: A single compound breaks down into two or more substances.
- General equation: AB → A + B
- Example: 2H2O → 2H2 + O2
Single Displacement (Substitution) Reactions: One element replaces another element in a compound.
- General equation: A + BC → AC + B
- Example: Zn + CuSO4 → ZnSO4 + Cu
Double Displacement (Exchange) Reactions: Two compounds exchange partners, resulting in the formation of two new compounds.
- General equation: AB + CD → AD + CB
- Example: NaCl + AgNO3 → NaNO3 + AgCl

Oxidation: The loss of one or more electrons by an atom, resulting in an increase in oxidation state.
Reduction: The gain of one or more electrons by an atom, resulting in a decrease in oxidation state.
Oxidation Numbers: A way to keep track of electrons during a reaction, using a set of rules to assign numbers to atoms.
Redox Reactions: Reactions that involve both oxidation and reduction, resulting in a transfer of electrons.
- Example: 2Cu + O2 → 2CuO (Cu is oxidized, O2 is reduced)

Balancing equations ensures that the number of atoms of each element is the same on both reactant and product sides, conserving mass and satisfying the Law of Conservation of Mass.
The steps to balance an equation involve writing the unbalanced equation, counting atoms, identifying unbalanced elements, adding coefficients, and checking the equation.
Coefficients are added to balance the equation, starting with the elements that appear most frequently.

Synthesis reactions involve the combination of two or more substances to form a new compound, with a general equation of A + B → AB.
Decomposition reactions involve the breakdown of a single compound into two or more substances, with a general equation of AB → A + B.
Single displacement reactions involve the replacement of one element with another in a compound, with a general equation of A + BC → AC + B.
Double displacement reactions involve the exchange of partners between two compounds, resulting in the formation of two new compounds, with a general equation of AB + CD → AD + CB.

Oxidation is the loss of one or more electrons by an atom, resulting in an increase in oxidation state.
Reduction is the gain of one or more electrons by an atom, resulting in a decrease in oxidation state.
Oxidation numbers are a way to keep track of electrons during a reaction, using a set of rules to assign numbers to atoms.
Redox reactions involve both oxidation and reduction, resulting in a transfer of electrons.
Examples of redox reactions include 2Cu + O2 → 2CuO, where Cu is oxidized and O2 is reduced.