ChemistryQ&A by dot point

Topic 1.5 Atomic Structure and Electron Configuration: write electron configurations for atoms and ions using the Aufbau principle, the Pauli exclusion principle, and Hund's rule, and relate them to the Coulombic model of the atom.

Topic 1.4 Composition of Mixtures: distinguish pure substances from mixtures and use elemental analysis and mass relationships to determine the composition of a mixture.

Topic 1.3 Elemental Composition of Pure Substances: calculate percent composition by mass and determine empirical and molecular formulas from experimental data.

Topic 1.2 Mass Spectra of Elements: interpret a mass spectrum to identify the isotopes of an element and their relative abundances, and calculate the average atomic mass from the data.

Topic 1.1 Moles and Molar Mass: use the mole and molar mass to convert between the mass of a pure substance, the number of moles, and the number of representative particles.

Topic 1.7 Periodic Trends: explain and predict the trends in atomic and ionic radius, ionization energy, and electronegativity using effective nuclear charge and shielding.

Topic 1.6 Photoelectron Spectroscopy: interpret a photoelectron spectrum to determine the relative energies of electrons in subshells and the number of electrons in each subshell, and relate it to electron configuration.

Topic 1.8 Valence Electrons and Ionic Compounds: relate the number of valence electrons to an element's group and reactivity, and predict the ions main-group elements form and the formulas of the ionic compounds they make.

Topic 2.2 Intramolecular Force and Potential Energy: interpret a potential-energy versus internuclear-distance curve to define bond length and bond energy, and explain how bond order, atomic size and charge affect bond strength.

Topic 2.5 Lewis Diagrams: draw Lewis diagrams for molecules and polyatomic ions, applying the octet rule and accounting for valence electrons, multiple bonds, and common exceptions.

Topic 2.6 Resonance and Formal Charge: draw resonance structures and use formal charge to select the most reasonable Lewis diagram, and explain how resonance describes delocalised bonding.

Topic 2.3 Structure of Ionic Solids: describe the lattice of an ionic solid, relate lattice energy to ionic charge and size using Coulomb's law, and explain the properties of ionic compounds from their structure.

Topic 2.4 Structure of Metals and Alloys: use the electron-sea model to explain metallic properties, and describe how interstitial and substitutional alloys change those properties.

Topic 2.1 Types of Chemical Bonds: classify bonds as ionic, covalent (polar or nonpolar), or metallic using electronegativity and the elements involved, and relate bond type to properties.

Topic 2.7 VSEPR and Bond Hybridization: use VSEPR theory to predict molecular geometry and bond angles, assign the hybridization of the central atom, and relate geometry to molecular polarity.

Topic 3.13 Beer-Lambert Law: use the Beer-Lambert law to relate the absorbance of a solution to its concentration, and apply a calibration to find an unknown concentration.

Topic 3.6 Deviation from Ideal Gas Law: explain why real gases deviate from the ideal gas law at high pressure and low temperature in terms of molecular volume and intermolecular forces.

Topic 3.4 Ideal Gas Law: use the ideal gas law and its partial-pressure and gas-density forms to relate the pressure, volume, temperature and amount of a gas in calculations.

Topic 3.1 Intermolecular Forces: identify and rank the intermolecular forces (London dispersion, dipole-dipole, hydrogen bonding, ion-dipole) present in a substance and relate their strength to properties such as boiling point and vapor pressure.

Topic 3.5 Kinetic Molecular Theory: state the postulates of kinetic molecular theory and use them to explain gas pressure, temperature, and the Maxwell-Boltzmann distribution of molecular speeds.

Topic 3.12 Photoelectric Effect: explain how the photoelectric effect demonstrates that light is quantised, using the threshold frequency and the relationship between photon energy and frequency.

Topic 3.2 Properties of Solids: relate the macroscopic properties of a solid (melting point, hardness, conductivity) to its type (ionic, metallic, covalent network, molecular) and the forces holding its particles together.

Topic 3.8 Representations of Solutions: use particulate-level diagrams to represent the species present in a solution, distinguishing strong electrolytes, weak electrolytes and nonelectrolytes.

Topic 3.9 Separation of Solutions and Mixtures (Chromatography): explain how chromatography, distillation and filtration separate the components of a mixture by exploiting differences in their interactions and properties.

Topic 3.3 Solids, Liquids, and Gases: describe the particle-level differences between the three states and explain how intermolecular forces and temperature determine which state a substance is in.

Topic 3.10 Solubility: explain solubility in terms of the intermolecular forces between solute and solvent (like dissolves like), and describe how temperature and pressure affect the solubility of solids and gases.

Topic 3.7 Solutions and Mixtures: define solute, solvent and solution, and calculate and use molarity to relate moles, volume and concentration, including dilutions.

Topic 3.11 Spectroscopy and the Electromagnetic Spectrum: relate the energy, frequency and wavelength of electromagnetic radiation and identify which type of molecular transition (rotational, vibrational, electronic) each region of the spectrum probes.

Topic 4.1 Introduction for Reactions: identify the evidence that a chemical reaction has occurred and distinguish chemical changes from physical changes at the macroscopic and particle levels.

Topic 4.8 Introduction to Acid-Base Reactions: apply the Bronsted-Lowry model to identify acids, bases and conjugate acid-base pairs, and write acid-base reactions as proton transfers.

Topic 4.6 Introduction to Titration: use titration data and reaction stoichiometry to determine the concentration of an unknown solution, distinguishing the equivalence point from the endpoint.

Topic 4.2 Net Ionic Equations: write balanced molecular, complete ionic and net ionic equations for reactions in aqueous solution, removing spectator ions.

Topic 4.9 Oxidation-Reduction (Redox) Reactions: assign oxidation numbers, identify the species oxidized and reduced and the oxidizing and reducing agents, and balance redox reactions using half-reactions.

Topic 4.4 Physical and Chemical Changes: distinguish physical changes (affecting intermolecular forces) from chemical changes (breaking and forming chemical bonds) and classify processes accordingly.

Topic 4.3 Representations of Reactions: connect symbolic, particulate and macroscopic representations of a reaction, using conservation of atoms to balance and interpret each.

Topic 4.5 Stoichiometry: use mole ratios from a balanced equation to relate amounts of reactants and products, and determine the limiting reactant, theoretical yield and percent yield.

Topic 4.7 Types of Chemical Reactions: classify reactions as precipitation, acid-base, or oxidation-reduction, and identify the driving force of each.

Topic 5.11 Catalysis: explain how a catalyst increases the rate by providing an alternative pathway with a lower activation energy, and distinguish homogeneous, heterogeneous and enzyme catalysis.

Topic 5.5 Collision Model: use collision theory and the Arrhenius equation to explain how activation energy, temperature, orientation and collision frequency control the rate constant.

Topic 5.3 Concentration Changes Over Time: use the integrated rate laws for zero-, first- and second-order reactions, identify order from a linear plot, and use the half-life of a first-order reaction.

Topic 5.4 Elementary Reactions: identify the molecularity of an elementary step and write its rate law directly from its stoichiometry, distinguishing elementary steps from overall reactions.

Topic 5.2 Introduction to Rate Law: write the rate law of a reaction, determine the reaction orders and the rate constant from initial-rate data, and interpret the meaning of order and the units of the rate constant.

Topic 5.7 Introduction to Reaction Mechanisms: represent a reaction as a sequence of elementary steps, identify reaction intermediates and catalysts, and confirm that the steps sum to the overall equation.

Topic 5.10 Multistep Reaction Energy Profile: interpret an energy diagram with more than one peak to identify intermediates, the activation energy of each step, and the rate-determining step.

Topic 5.9 Pre-Equilibrium Approximation: derive the rate law of a mechanism with a fast initial equilibrium followed by a slow step by expressing the intermediate concentration in terms of reactant concentrations.

Topic 5.6 Reaction Energy Profile: interpret a potential-energy diagram to identify the activation energy of the forward and reverse reactions, the transition state and the enthalpy of reaction.

Topic 5.8 Reaction Mechanism and Rate Law: identify the rate-determining (slow) step of a mechanism and use it to write the rate law, and check a proposed mechanism against the experimental rate law.

Topic 5.1 Reaction Rates: express the rate of a reaction in terms of the change in concentration of a reactant or product over time, relate rates through the stoichiometric coefficients, and identify the factors that influence rate.

Topic 6.7 Bond Enthalpies: estimate the enthalpy change of a reaction from average bond enthalpies, using the rule that breaking bonds absorbs energy and forming bonds releases it.

Topic 6.1 Endothermic and Exothermic Processes: classify a process as endothermic or exothermic from the direction of energy flow, the sign of the enthalpy change and the bonds broken and formed.

Topic 6.2 Energy Diagrams: draw and interpret an energy diagram showing the relative enthalpies of reactants and products and the enthalpy change of the reaction.

Topic 6.5 Energy of Phase Changes: explain why temperature is constant during a phase change, interpret a heating curve, and calculate the energy of a phase change from the enthalpy of fusion or vaporisation.

Topic 6.8 Enthalpy of Formation: use standard enthalpies of formation to calculate the enthalpy of a reaction as the sum for products minus the sum for reactants.

Topic 6.4 Heat Capacity and Calorimetry: use the equation q equals mc delta T with specific heat capacity, and use calorimetry data to determine the heat of a process.

Topic 6.3 Heat Transfer and Thermal Equilibrium: explain heat transfer as the flow of energy from a hotter object to a cooler one until thermal equilibrium is reached, relating it to the kinetic energy of particles.

Topic 6.9 Hess's Law: use Hess's law to determine the enthalpy of a reaction by combining the enthalpies of a series of reactions that add to the target, reversing and scaling as needed.

Topic 6.6 Introduction to Enthalpy of Reaction: interpret the enthalpy of reaction as a state function and use thermochemical equations to relate the heat of a reaction to the amount of substance reacted.

Topic 7.7 Calculating Equilibrium Concentrations: use an ICE table and the value of K to calculate equilibrium concentrations, including the use of the small-x (5%) approximation where valid.

Topic 7.4 Calculating the Equilibrium Constant: calculate the value of an equilibrium constant from equilibrium concentrations or pressures, using an ICE table where initial and equilibrium data are mixed.

Topic 7.12 Common-Ion Effect: explain and calculate the reduced solubility of a salt in a solution that already contains one of its ions, using Le Chatelier's principle and Ksp.

Topic 7.2 Direction of Reversible Reactions: relate the direction of a reversible reaction to the relative magnitudes of the forward and reverse rates as the system approaches equilibrium.

Topic 7.14 Free Energy of Dissolution: relate the thermodynamic favourability of dissolving a salt to the enthalpy and entropy of dissolution and to the sign of the free energy change.

Topic 7.1 Introduction to Equilibrium: describe dynamic equilibrium as the state in which the forward and reverse reaction rates are equal and concentrations are constant, at the particle level.

Topic 7.9 Introduction to Le Chatelier's Principle: predict the direction a system at equilibrium shifts in response to a change in concentration, volume or pressure, or temperature, using Le Chatelier's principle.

Topic 7.11 Introduction to Solubility Equilibria: write the solubility product expression Ksp for a slightly soluble salt and relate Ksp to molar solubility and ion concentrations.

Topic 7.5 Magnitude of the Equilibrium Constant: interpret the size of an equilibrium constant as a measure of the extent of reaction, relating large, small and intermediate K to the dominant species at equilibrium.

Topic 7.13 pH and Solubility: explain why the solubility of salts of weak acids or bases depends on pH, using Le Chatelier's principle applied to the dissolution and acid-base equilibria.

Topic 7.6 Properties of the Equilibrium Constant: determine how K changes when a reaction is reversed (reciprocal), scaled (power) or combined with another reaction (product), and relate Kc to Kp.

Topic 7.3 Reaction Quotient and Equilibrium Constant: write the expression for the reaction quotient Q and the equilibrium constant K, and compare Q with K to predict the direction of reaction.

Topic 7.10 Reaction Quotient and Le Chatelier's Principle: explain the direction of an equilibrium shift quantitatively by comparing the reaction quotient Q with K after a disturbance.

Topic 7.8 Representations of Equilibrium: interpret and construct particulate diagrams and concentration-versus-time graphs that represent a system at equilibrium and the relative amounts of reactants and products.

Topic 8.4 Acid-Base Reactions and Buffers: predict the products of acid-base reactions, identify the salts formed, and explain how a buffer made from a weak acid and its conjugate base resists pH change.

Topic 8.5 Acid-Base Titrations: interpret titration curves to find the equivalence point and pH at key points, and use the half-equivalence point to find pKa for a weak acid.

Topic 8.1 Introduction to Acids and Bases: identify Bronsted-Lowry acids, bases and conjugate acid-base pairs, and distinguish strong from weak acids and bases.

Topic 8.6 Molecular Structure of Acids and Bases: explain trends in acid strength in terms of bond strength, bond polarity, electronegativity and the stability of the conjugate base.

Topic 8.7 pH and pKa: use the Henderson-Hasselbalch equation to relate the pH of a buffer to the pKa and the ratio of conjugate base to weak acid, and explain buffer capacity.

Topic 8.2 pH and pOH of Strong Acids and Bases: calculate pH and pOH from concentration for strong acids and bases, using the autoionisation of water and the relationship pH plus pOH equals 14 at 25 degrees Celsius.

Topic 8.3 Weak Acid and Base Equilibria: use Ka or Kb with an ICE table to calculate the pH and percent ionization of a weak acid or base, and relate Ka, Kb and Kw.

Topic 9.2 Absolute Entropy and Entropy Change: use standard molar entropies to calculate the standard entropy change of a reaction as the sum for products minus the sum for reactants.

Topic 9.9 Cell Potential and Free Energy: calculate the standard cell potential from standard reduction potentials, and relate it to the free energy change with delta G standard equals minus n F E standard.

Topic 9.10 Cell Potential Under Nonstandard Conditions: predict how the cell potential changes with concentration using the Nernst relationship qualitatively, and explain why a cell potential falls to zero at equilibrium.

Topic 9.7 Coupled Reactions: explain how an unfavorable reaction can be driven by coupling it to a favorable reaction so that the combined free energy change is negative.

Topic 9.11 Electrolysis and Faraday's Law: use the current, time and the moles of electrons to calculate the mass or amount of substance produced at an electrode during electrolysis.

Topic 9.5 Free Energy and Equilibrium: relate the standard free energy change to the equilibrium constant using delta G standard equals minus RT ln K, and use delta G equals delta G standard plus RT ln Q for non-standard conditions.

Topic 9.6 Free Energy of Dissolution: analyze the dissolution of a salt using delta G equals delta H minus T delta S, and relate the sign of delta G to whether and how much the salt dissolves.

Topic 9.8 Galvanic (Voltaic) and Electrolytic Cells: describe the structure and operation of galvanic and electrolytic cells, identifying the anode, cathode, electron flow and the direction of energy conversion.

Topic 9.3 Gibbs Free Energy and Thermodynamic Favorability: use the equation delta G equals delta H minus T delta S to determine thermodynamic favourability and the temperature dependence of spontaneity.

Topic 9.1 Introduction to Entropy: describe entropy as a measure of the dispersal of energy and matter, and predict the sign of the entropy change for physical and chemical processes.

Topic 9.4 Thermodynamic and Kinetic Control: distinguish thermodynamic favourability (sign of delta G) from kinetic feasibility (rate), and explain why a favorable reaction may be slow.