Unit 4 - Stoichiometry of Chemical Reactions

Acid

Substance that produces H₃O⁺ (hydronium ions) in water

example) HCl

Base

Substance that produces OH⁻ (hydroxide ions) in water

example) NaOH in water

Acid-Base Reaction

Reaction where a hydrogen ion (H⁺) is transferred between substances

example) HCl + NaOH → NaCl + H₂O

Balanced Equation

Chemical equation with the same number of atoms for each element on both sides

example) 2H₂ + O₂ → 2H₂O

Chemical Equation

Symbolic way to show a chemical reaction

example) CH₄ + 2O₂ → CO₂ + 2H₂O

Coefficient

Number before a chemical formula showing how many units are involved

example) 2H₂O means 2 molecules of water

Combustion Reaction

Reaction where a substance reacts with oxygen to release energy as heat/light

example) Burning propane

Limiting Reactant

The reactant that runs out first and limits how much product can form

example) If 10 buns and 8 patties → 8 burgers made

Excess Reactant

The reactant left over after the reaction is complete

example) Extra buns left from the burger analogy

Product

The substance formed in a chemical reaction

example) CO₂ and H₂O are products of combustion

Reactant

The starting substance in a chemical reaction

example) CH₄ and O₂ in combustion

Neutralization Reaction

Reaction between an acid and base to form salt and water

example) HCl + NaOH → NaCl + H₂O

Precipitate

Solid that forms from two solutions reacting

example) Mixing AgNO₃ and NaCl forms AgCl precipitate

Precipitation Reaction

Reaction where an insoluble solid forms from soluble reactants

example) AgNO₃ + NaCl → AgCl + NaNO₃

Oxidation

Loss of electrons or increase in oxidation number

example) Na → Na⁺ + e⁻

Reduction

Gain of electrons or decrease in oxidation number

example) Cl₂ + 2e⁻ → 2Cl⁻

Redox Reaction (Oxidation-Reduction Reaction)

Reaction involving both oxidation and reduction

example) Zn + Cu²⁺ → Zn²⁺ + Cu

Oxidizing Agent

Substance that causes oxidation (it gets reduced)

example) O₂ in combustion

Reducing Agent

Substance that causes reduction (it gets oxidized)

example) Zn in Zn + Cu²⁺ → Zn²⁺ + Cu

Stoichiometry

Relationship between amounts of reactants and products using a balanced equation

example) 2H₂ + O₂ → 2H₂O means 2 moles H₂ make 2 moles H₂O

Theoretical Yield

Maximum amount of product that can form from given reactants

example) Perfect calculation with no losses

Actual Yield

Amount of product actually produced in a reaction
example) Lab experiment gives less than predicted

Percent Yield

Measure of efficiency, actual yield ÷ theoretical yield × 100

example) 80% yield means you got 80% of what was expected