Chemical Reactions and Equations

Study Notes

Chemical Equation

A chemical equation is a symbolic representation of a chemical reaction
It represents the reactants, products, and their respective quantities
The reactants are written on the left-hand side, and the products are written on the right-hand side
The arrow (→) is used to separate the reactants from the products

Types of Chemical Reactions

Combination Reaction: A reaction in which two or more substances combine to form a new substance
- Example: 2H2 + O2 → 2H2O
Decomposition Reaction: A reaction in which a single substance breaks down into two or more substances
- Example: 2H2O → 2H2 + O2
Displacement Reaction: A reaction in which one element displaces another element from a compound
- Example: Zn + CuSO4 → ZnSO4 + Cu
Oxidation and Reduction: A reaction in which one substance loses electrons (oxidation) and another substance gains electrons (reduction)
- Example: 2CuO + H2 → 2Cu + H2O (CuO is reduced, H2 is oxidized)

Chemical Reaction Rates

Factors Affecting Reaction Rates:
- Concentration of reactants
- Temperature
- Surface area of reactants
- Presence of catalysts
Catalysts: Substances that increase reaction rates without being consumed by the reaction
- Examples: enzymes, vanadium(V) oxide (V2O5)

Exothermic and Endothermic Reactions

Exothermic Reaction: A reaction that releases heat energy
- Example: combustion of fuels
Endothermic Reaction: A reaction that absorbs heat energy
- Example: photosynthesis in plants

Combination Reaction: two or more substances combine to form a new substance (2H2 + O2 → 2H2O)
Decomposition Reaction: a single substance breaks down into two or more substances (2H2O → 2H2 + O2)
Displacement Reaction: one element displaces another from a compound (Zn + CuSO4 → ZnSO4 + Cu)
Oxidation and Reduction: one substance loses electrons (oxidation) and another gains electrons (reduction) (2CuO + H2 → 2Cu + H2O)

Factors Affecting Reaction Rates:
- Concentration of reactants
- Temperature
- Surface area of reactants
- Presence of catalysts
Catalysts: substances that increase reaction rates without being consumed (enzymes, vanadium(V) oxide (V2O5))

A combination reaction occurs when two or more substances combine to form a new substance, such as 2H2 + O2 → 2H2O.
In a decomposition reaction, a single substance breaks down into two or more substances, such as 2H2O → 2H2 + O2.
A displacement reaction involves one element displacing another element from a compound, such as Zn + CuSO4 → ZnSO4 + Cu.
In a double displacement reaction, two compounds exchange partners, resulting in the formation of two new compounds, such as NaCl + AgNO3 → NaNO3 + AgCl.
Oxidation-reduction reactions involve the gain or loss of electrons, such as 2Mg + O2 → 2MgO, where Mg loses electrons and O2 gains electrons.

Reactants are the substances that undergo a chemical change.
Products are the substances formed as a result of a chemical change.
A chemical equation is a representation of a chemical reaction using chemical formulas and symbols.
The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction.

Increasing the concentration of reactants can increase the rate of reaction.
Higher temperatures can increase the rate of reaction.
A catalyst is a substance that speeds up a chemical reaction without being consumed.
Increasing the surface area of reactants can increase the rate of reaction.

The mole ratio is the ratio of the number of moles of reactants to the number of moles of products.
A mole formula shows the number of moles of each element in a compound.
The empirical formula shows the simplest whole-number ratio of atoms of each element in a compound.