Skip to content
Start free

General Chemistry

College9 units and 96 lessons. Helio talks each one through and draws each step on a board.

Start free

Units

  1. Atomic structure and properties

    8 lessons
    1. Moles and Molar MassConvert a measured mass to molecules or specified atoms, showing units that cancel.
    2. Mass Spectra of ElementsRead isotope peaks, calculate average atomic mass, and justify which isotope is more abundant.
    3. Elemental Composition of Pure SubstancesCalculate empirical and molecular formulas from elemental mass percentages and molar mass.
    4. Composition of MixturesCalculate a component’s mass percent from elemental analysis and use chlorine percentages to evaluate purity claims.
    5. Atomic Structure and Electron ConfigurationWrite ground-state configurations for atoms and ions; explain electron removal using shell position, shielding, and Coulomb’s law.
    6. Photoelectron SpectroscopyIdentify a neutral atom from its PES peaks and explain peak positions using electron–nucleus attraction.
    7. Periodic TrendsJustify trends in atomic radius, ionization energy, electronegativity, and ion size using electron structure and attraction.
    8. Valence Electrons and Ionic CompoundsPredict typical ion charges and ionic formulas; explain group analogies and contrasting metal and halogen reactivity trends.

  2. Compound structure and properties

    8 lessons
    1. Types of Chemical BondsClassify bonding and justify each choice using electron attraction, particle models, and observed properties.
    2. Intramolecular Force and Potential EnergySketch energy–distance curves, read bond length and bond energy, and explain differences between curves.
    3. Structure of Ionic SolidsDraw an ionic lattice and use ion arrangement, charge, size, and mobility to explain its properties.
    4. Structure of Metals and AlloysUse particle diagrams and atomic radii to explain metallic conductivity and differences in alloy malleability.
    5. Lewis DiagramsDraw complete Lewis diagrams for molecules and ions, accounting for every valence electron.
    6. Resonance and Formal ChargeDraw resonance structures, explain equal bond lengths, calculate formal charges, and identify favored Lewis structures.
    7. VSEPR: electron-domain and molecular geometry, including expanded octetsPredict electron-domain geometry, molecular geometry and approximate bond angles from a Lewis diagram, including expanded octets such as SF₄, ClF₃, XeF₂ and XeF₄.
    8. Polarity, hybridization and sigma/pi bondsDecide whether a molecule is polar from its shape, assign sp, sp² or sp³ to an atom from its domain count, and count σ and π bonds in a Lewis diagram.

  3. Properties of substances and mixtures

    14 lessons
    1. Identifying the forces: dispersion, dipole-dipole, hydrogen bonding, ion-dipoleName every attraction between particles in a pure substance or a mixture, draw hydrogen bonds and ion-dipole attractions with the correct ends facing, and say what boiling overcomes.
    2. Ranking and justifying boiling point, vapor pressure and solubilityCompare substances by naming the forces in each, judging which are stronger and why, and linking the result to boiling point, vapor pressure and solubility.
    3. Properties of SolidsExplain a solid’s melting behavior, conductivity, and order from its particles and attractions.
    4. Solids, Liquids, and GasesDraw particle models of three phases and explain phase changes, steam’s volume, and why ice floats.
    5. Ideal Gas LawCalculate gas properties and partial pressures, and explain changes using the quantities held constant.
    6. Kinetic Molecular TheoryExplain gas pressure, compare particle speeds, and interpret speed-distribution curves using a particle model.
    7. Deviation from Ideal Gas LawExplain whether a gas deviates above or below ideal behavior using particle reasoning and PV/(nRT).
    8. Solutions and MixturesCalculate molarity, ion concentrations, preparation mass, and dilution; explain each using particles and finished solution volume.
    9. Representations of SolutionsDraw and interpret aqueous solutions with correct particles, water orientation, ion ratios, and relative concentration.
    10. Separation of Solutions and MixturesExplain how attractions separate dyes, calculate Rf, and predict which liquid is enriched in a first distillate.
    11. SolubilityPredict relative solubility and justify it with particle attractions; predict how pressure and temperature affect dissolved CO₂.
    12. Spectroscopy and the Electromagnetic SpectrumPredict which transition light can cause and explain infrared absorption and solution colour.
    13. Properties of PhotonsCalculate photon energy per photon or mole, and explain emission lines and photoelectric results.
    14. Beer-Lambert LawCalculate concentration from absorbance and explain how wavelength, path length, or a lab error changes the result.

  4. Chemical reactions

    10 lessons
    1. Introduction for ReactionsClassify chemical and physical changes by identifying whether new substances form.
    2. Net Ionic EquationsWrite balanced net ionic equations for reactions and physical dissolving.
    3. Representations of ReactionsDraw an after-reaction particle box from a balanced equation and starting counts, including leftover reactants.
    4. Physical and Chemical ChangesClassify changes and justify each claim by identifying what happens to particles, bonds, and attractions.
    5. Mole ratios and limiting reactantConvert reactant masses to moles, use a balanced-equation mole ratio, find the limiting reactant, and calculate theoretical yield and the excess reactant left.
    6. Stoichiometry through solutions and gases; percent yieldGet moles from a gas volume or a solution, carry them through a balanced equation to the limiting reactant and the final amounts, draw the before and after particles, and calculate percent yield.
    7. Introduction to TitrationCalculate an acid’s concentration or molar mass from titration data and predict how measurement errors affect the result.
    8. Types of Chemical ReactionsClassify reactions as acid–base, redox, or precipitation and justify each with the particles that change.
    9. Introduction to Acid-Base ReactionsWrite proton-transfer equations and identify acids, bases, and conjugate pairs.
    10. Oxidation-Reduction (Redox) ReactionsBalance a redox equation in acidic solution using half-reactions, then justify the equation using atoms, charge, and electrons.

  5. Kinetics

    12 lessons
    1. Reaction RatesCalculate positive reaction rates from concentration–time data, relate species rates through coefficients, and choose measurements that track a reaction.
    2. Introduction to Rate LawDetermine a rate law from initial-rate data, then calculate and use k with correct units.
    3. First-order kinetics and half-lifeShow a reaction is first order from concentration-time data, find k, use the half-life, and predict a concentration or a time from the first-order law.
    4. Zero and second order: choosing order from linear plotsDecide the order of a reaction from which of [A], ln[A] or 1/[A] is straight against time, find k from the slope with its sign and units, and use successive half-lives to check the order.
    5. Elementary ReactionsWrite the rate law and molecularity of a given elementary step; explain why an overall equation cannot establish its rate law.
    6. Collision ModelExplain rate changes using collision frequency, collision energy, and orientation.
    7. Reaction Energy ProfileInterpret a reaction energy profile, calculate its energy changes, and explain how its barrier affects rate.
    8. Introduction to Reaction MechanismsAdd elementary steps, distinguish intermediates from catalysts, and evaluate evidence for a proposed mechanism.
    9. Reaction Mechanism and Rate LawDerive a rate law when the first step is slow and test whether a mechanism agrees with experiment.
    10. Pre-Equilibrium ApproximationDerive a rate law from a fast reversible step followed by a slow step, without leaving an intermediate in the final law.
    11. Multistep Reaction Energy ProfileDraw and read a profile that matches its mechanism, slow step, and overall ΔH.
    12. CatalysisExplain how catalysts increase reaction rates, participate in mechanisms, and leave ΔH and K unchanged.

  6. Thermochemistry

    9 lessons
    1. Endothermic and Exothermic ProcessesClassify energy transfer from a temperature change and explain it using particle attractions.
    2. Energy DiagramsDraw an energy diagram from ΔH and explain its sign and a surroundings-temperature observation.
    3. Heat Transfer and Thermal EquilibriumExplain heat transfer through particle interactions and use energy conservation to find a shared final temperature.
    4. Heat Capacity and CalorimetryCalculate molar enthalpy from coffee-cup data and explain how heat loss affects the result.
    5. Energy of Phase ChangesCalculate heat absorbed or released during phase changes and explain constant temperature and heat signs.
    6. Introduction to Enthalpy of ReactionCalculate heat released or absorbed from an amount of reactant, and adjust reaction enthalpy when equations or states change.
    7. Bond EnthalpiesEstimate a gas-phase reaction’s ΔH from Lewis structures and bond enthalpies.
    8. Enthalpy of FormationCalculate reaction enthalpy from formation enthalpies and explain why the calculation is products minus reactants.
    9. Hess's LawFind a target reaction’s ΔH by adjusting and adding known reactions.

  7. Equilibrium

    12 lessons
    1. Introduction to EquilibriumExplain equilibrium using concentration readings, reaction rates, and a particle picture.
    2. Direction of Reversible ReactionsPredict net direction from reaction rates and explain how either starting side approaches equilibrium.
    3. Reaction Quotient and Equilibrium ConstantWrite K and Q expressions, then compare Q with K to predict net reaction direction.
    4. Calculating the Equilibrium ConstantCalculate Kc from equilibrium data or an ICE table, and calculate Kp for gases.
    5. Magnitude of the Equilibrium ConstantUse K and its expression to describe equilibrium composition without inferring reaction speed.
    6. Properties of the Equilibrium ConstantCalculate K for a target reaction by reversing, scaling, and adding known equilibrium equations.
    7. Calculating Equilibrium ConcentrationsCalculate equilibrium concentrations from starting concentrations and Kc, choosing a valid method and checking approximations.
    8. Representations of EquilibriumUse particle diagrams to identify equilibrium, predict net change, and explain why steady counts do not mean stopped reactions.
    9. Introduction to Le Chatelier's PrinciplePredict and justify an equilibrium shift, or no shift, after a stated change.
    10. Reaction Quotient and Le Chatelier's PrincipleCalculate Q after a change and justify the net reaction direction by comparing Q with K.
    11. Introduction to Solubility EquilibriaCalculate molar solubility and Ksp, compare salts fairly, and predict precipitation using Q.
    12. Common-Ion EffectCalculate molar solubility with a common ion and explain precipitation using Q and Ksp.

  8. Acids and bases

    12 lessons
    1. Introduction to Acids and BasesCalculate water-ion concentrations, pH, and pOH at a stated temperature; explain neutrality.
    2. pH and pOH of Strong Acids and BasesCalculate pH from strong acid and base concentrations, accounting for hydroxide count, dilution, and water’s ions when necessary.
    3. Weak Acid and Base EquilibriaCalculate weak-acid and weak-base pH, check approximations, and relate ionization to concentration and conjugate strength.
    4. Acid-Base Reactions and BuffersFind what remains after an acid-base reaction and decide whether the mixture is a buffer.
    5. Titration curves: strong/strong vs weak acid/strong base, pH at the four key pointsCalculate the equivalence volume, the pH at the four key points of a strong acid and a weak acid titrated with a strong base, and read pKₐ from the half-equivalence point.
    6. Weak base/strong acid and polyprotic curves, indicator selection, species in the flaskFind the pH at the key points of a weak base titrated with a strong acid and of a diprotic acid, choose an indicator from the steep window, draw the species in the flask, and judge how a lab error changes a calculated concentration.
    7. Molecular Structure of Acids and BasesPredict relative acid or base strength from molecular structure and support each prediction with structural evidence.
    8. pH and pKaPredict a weak acid’s predominant form and calculate its deprotonated-to-protonated ratio from pH and pKa.
    9. Properties of BuffersExplain with particles and net ionic equations why small acid or base additions change a buffer’s pH only slightly.
    10. Henderson-Hasselbalch EquationCalculate buffer pH, update it after an addition, and choose a ratio for a target pH.
    11. Buffer CapacityPredict and calculate how buffer amounts, component ratios, and dilution affect resistance to added acid or base.
    12. pH and SolubilityPredict how pH changes a salt’s solubility and justify the prediction using its anion and Q versus Kₛₚ.

  9. Thermodynamics and electrochemistry

    11 lessons
    1. Introduction to EntropyPredict and justify entropy changes using particle arrangements, phase, gas moles, and molecular complexity.
    2. Absolute Entropy and Entropy ChangeCalculate reaction entropy change from standard molar entropies, using coefficients and correct units.
    3. Gibbs Free Energy and Thermodynamic FavorabilityCalculate ΔG° from enthalpy and entropy or formation values, then justify how temperature affects favourability.
    4. Thermodynamic and Kinetic ControlExplain why a favoured reaction can be slow and predict what a catalyst changes.
    5. Free Energy and EquilibriumCalculate K from ΔG° and explain why actual ΔG, not ΔG°, is zero at equilibrium.
    6. Free Energy of DissolutionExplain dissolution using ΔH°soln, ΔS°soln, and ΔG°soln, then connect ΔG°soln to an equilibrium constant.
    7. Coupled ReactionsAdd linked reactions, calculate overall ΔG°, and explain how chemical or external energy drives an uphill process.
    8. Galvanic (Voltaic) and Electrolytic CellsLabel both cell types, write their reactions, and explain electron flow, ion flow, and electrode mass changes.
    9. Cell Potential and Free EnergyCalculate standard cell potential and free-energy change, then use their signs to compare K with 1.
    10. Cell Potential Under Nonstandard ConditionsUse Q to justify changes in cell voltage, explain why a cell runs down, and identify a concentration cell’s cathode.
    11. Electrolysis and Faraday's LawCalculate electrolysis product mass or running time and identify reactions at each electrode.

More courses

All science courses

A tutor you can talk to

45 minutes every month. No card.

Start free