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Chemistry

The mole and stoichiometry

Moles, molar mass, empirical formulas, and yield.

Basics

Mole

One mole is Avogadro’s number of particles (about 6.022×10²³). Mass (g) = moles × molar mass (g/mol). For gases, molar volume is about 22.4 L/mol near STP — check the STP definition in use.

Limiting reactant

Convert to moles, apply the coefficient ratio, and the reactant that runs out first sets the product amount. The rest is in excess.

Formulas

Amount in moles

n = m / M

Mass divided by molar mass.

Symbols

  • n amount (mol)
  • m mass (g)
  • M molar mass (g/mol)

Mass percent

%X = (m_X / m_total) × 100%

Mass fraction of element X in a compound.

Symbols

  • m_X mass of element X
  • m_total total mass

Percent yield

%yield = (actual / theoretical) × 100%

Actual product versus the stoichiometric maximum.

Symbols

  • actual actual yield
  • theoretical theoretical yield

Molarity

c = n / V

Moles of solute per litre of solution.

Symbols

  • c molarity (mol/L, M)
  • n moles of solute
  • V solution volume (L)

Dilution

c₁ V₁ = c₂ V₂

Same moles of solute; add solvent only.

Symbols

  • c₁, V₁ initial concentration and volume
  • c₂, V₂ final concentration and volume

In this field

Chemistry

Atoms and the periodic table

Atomic structure, nucleus and electrons, periods and groups.

 Chemistry

Chemical bonding

Ionic, covalent, and metallic bonds, plus molecular shape.

 Chemistry

Gases and acids–bases

Ideal gas, pH, and buffers.

 Chemistry

Thermo, equilibrium, kinetics

Enthalpy, Gibbs energy, K, and rate laws.

 Chemistry

Electrochemistry and organic basics

Oxidation numbers, cells, Nernst, functional groups.

 Chemistry

Nuclear chemistry

Radioactivity, half-life, binding energy.

 Chemistry

Solutions and kinetics

Concentration, colligative properties, rate laws.

 Chemistry

Analytical chemistry

Titration, spectroscopy, and chromatography — measuring what is present and how much.

 Chemistry

Polymers and solids

Crystals and glasses, metal–ionic–covalent solids, polymer chains and the glass transition.

 Chemistry

Coordination compounds

Ligands, coordination number, crystal field, colour, and an 18-electron sketch.

 Chemistry

Electrochemical cells

Galvanic versus electrolytic, Nernst, Faraday, and a corrosion sketch.

 Chemistry

Phase equilibria and diagrams

Gibbs phase rule, unary diagrams, eutectics, and the lever rule.