Unit 4 Complete Guide: Reaction Types, Stoichiometry, and Analysis

Chemical Reactions

Involve the breaking and forming of intramolecular bonds to create new substances.

Physical Changes

Involve changes in intermolecular forces without changing the chemical composition.

Evidence of a Chemical Reaction

Observations suggesting a chemical change, such as production of heat, gas formation, solid precipitate, or color change.

Molecular Equation

Shows the complete formulas of all reactants and products in a chemical reaction.

Complete Ionic Equation

Shows all strong electrolytes dissociated into ions with solids, liquids, and gases intact.

Net Ionic Equation

Removes spectator ions to show only the species that are actually reacting.

Spectator Ions

Ions that appear unchanged on both sides of a chemical equation.

SNAP Rule

A mnemonic for soluble salts: Sodium (Na+), Nitrate (NO3-), Ammonium (NH4+), Potassium (K+).

Balancing Chemical Equations

Ensuring atom counts match on both sides, based on the Law of Conservation of Mass.

Limiting Reactant

The reagent that is completely consumed first, limiting the amount of product formed.

Percent Yield Formula

Percent Yield = (Actual Yield / Theoretical Yield) x 100%.

Combustion Reaction

A hydrocarbon reacts with oxygen to produce carbon dioxide and water.

Precipitation Reactions

Occur when two aqueous solutions mix to form an insoluble solid.

Neutralization Reaction

An acid-base reaction involving the transfer of protons (H+).

Acid (Bronsted-Lowry)

A proton (H+) donor.

Base (Bronsted-Lowry)

A proton (H+) acceptor.

Conjugate Acid-Base Pair

Species formed when an acid donates a proton and a base accepts it.

Amphoteric Substances

Substances that can act as either an acid or a base depending on the environment.

Oxidation-Reduction (Redox) Reactions

Involve the transfer of electrons, tracked using oxidation numbers.

LEO the lion says GER

Mnemonic for oxidation (Lose Electrons) and reduction (Gain Electrons).

Equivalence Point in Titrations

The point where moles of titrant equal moles of analyte.

End Point in Titrations

The point where the indicator changes color in a titration.

Gravimetric Analysis

A method to determine concentration by measuring mass, typically involving precipitation.

Titration Calculation (1:1 ratio)

Macid * Vacid = Mbase * Vbase.

Potassium (K) Molar Mass

Approximately 39.10 g/mol based on periodic table.

Diatomic Elements

Elements such as O2, N2, and H2 that exist in pairs when in their elemental form.

Collision Theory

For a reaction to occur, molecules must collide with the correct orientation and sufficient energy.

Stoichiometry

The mathematics of chemical reactions based on the conservation of mass.

Common Mistake in Titration

Misreading the buret volume or forgetting to rinse the buret with titrant.

Common Mistake in Gravimetric Analysis

Not drying the precipitate, leading to inaccurate mass measurements.

Oxidation State of Elements

Neutral atoms have an oxidation state of 0.

Oxidation State of Monatomic Ions

Equal to their charge.

Hydrogen in Oxidation States

+1 with nonmetals, -1 with metals.

Oxygen in Oxidation States

Usually -2, except in peroxides where it's -1.

Carbon in Combustion Rule

All carbon from the original compound ends up in CO2.

Hydrogen in Combustion Rule

All hydrogen from the original compound ends up in H2O.

Calculating Molar Mass

Determining molar mass as mass divided by moles.

Neutralization Example Reaction

HC2H3O2 + H2O ↔ C2H3O2- + H3O+.

Stoichiometric Ratio in Reactions

The coefficient ratio from the balanced equation used for mole conversions.

Common Pitfall: Redox

Confusion between oxidation state and ionic charge.

Common Pitfall: Solubility

Assuming common ions like Cl- are always soluble.

Common Pitfall: Balancing Equations

Forgetting to balance the equation before performing stoichiometric calculations.

Common Pitfall: Gases

Forgetting that certain elements are diatomic in their elemental state.