Chemical Reactions and Balanced Equations

Chemical Reactions and Balanced Equations

• A chemical reaction is a process where reactants change into products, involving the formation and breaking of chemical bonds.
• Reactants are the starting materials in a chemical reaction.
• Products are the new substances formed during a chemical reaction.

Characteristics of Chemical Reactions

• Change of state: A physical change in the state of matter (e.g., solid to liquid).
• Change in colour: A visible change in the colour of the substances.
• Formation of a precipitate: The formation of a solid from a solution.
• Change in temperature: A change in the temperature of the reaction mixture (e.g., heating or cooling).
• Evolution of gas: The release of gas bubbles from the reaction mixture.

Reversible and Irreversible Reactions

• Reversible reaction: A reaction that can proceed in both the forward and backward directions (indicated by a double-headed arrow).
• Irreversible reaction: A reaction that proceeds only in one direction (indicated by a single-headed arrow).

Types of Chemical Reactions

• Combination reaction: Two or more reactants combine to form a single product.
• Decomposition reaction: A single reactant breaks down into two or more simpler products.
• Displacement reaction: One element replaces another element in a compound. This can be single or double displacement.

Chemical Equations

• Chemical equations use chemical symbols to represent chemical reactions.
• A balanced chemical equation shows the same number of atoms of each element on both sides of the equation.

Stoichiometry

• Stoichiometry is the study of quantitative relationships (ratios) between substances in a chemical reaction.
• Stoichiometry calculations often involve the mass or volume of reactants and products.

Mole Concept

• A mole is the amount of a substance containing a standard number of particles.
• Avogadro's number is the constant representing the number of particles in a mole of a substance (approximately 6.02 x 10²³).
• Moles act as a bridge between molecular scale and real-world scale.

Additional Reaction Types

• Precipitation reaction: Formation of a solid from the mix of solutions.
• Combustion reaction: A reaction with oxygen that often produces heat and light.
• Redox reaction: A reaction involving the transfer of electrons.
• Neutralization reaction: A reaction between an acid and a base resulting in the formation of a salt and water.

States of Matter in Equations

• (s) = solid
• (l) = liquid
• (g) = gas
• (aq) = aqueous solution (dissolved in water)
• (conc.) = concentrated
• (dil.) = dilute
• (ppt) = precipitate