Physical Chemistry Problem Solving

80 lessons, pages 2401–2480.

  1. A Physical-Chemistry Calculation Map — Choosing quantities, equations and checks before arithmetic
  2. Units as Algebraic Evidence — Using dimensions to detect invalid substitutions
  3. Significant Figures in Multi-Step Problems — Keeping guard digits and reporting justified precision
  4. Estimating an Answer before Calculation — Orders of magnitude and limiting-case checks
  5. Mass Balance across Linked Steps — Conservation tables for sequential operations
  6. Charge Balance in Aqueous Mixtures — Electroneutrality as a numerical constraint
  7. Choosing a Convenient Calculation Basis — One mole, one litre and one hundred gram strategies
  8. Ratios, Fractions and Percentages — Avoiding denominator errors in composition data
  9. Uncertainty and Sensitivity in Derived Results — How input precision affects computed chemistry
  10. Diagnosing Impossible Numerical Answers — Bounds from conservation, positivity and limiting cases
  11. Moles, Entities and Formula Units — Converting mass to the correct counted species
  12. Empirical Formula from Composition Data — Mole-ratio inference with rounding checks
  13. Molecular Formula from Empirical Mass — Matching an integer multiple to measured molar mass
  14. Combustion Analysis with Oxygen Difference — Recovering C, H and O amounts from product masses
  15. Reaction Extent and Coefficient Ratios — One extent variable for every reacting species
  16. Limiting Reagent in a Three-Reactant Mixture — Comparing available amount per stoichiometric coefficient
  17. Excess Reagent and Final Composition — Subtracting reacted amounts after finding the limiting extent
  18. Purity Corrections before Stoichiometry — Separating active reactant from inert sample mass
  19. Yield and Selectivity in Linked Reactions — Distinguishing conversion, desired-product yield and side products
  20. Sequential-Reaction Mole Accounting — Carrying intermediate amounts through two balanced equations
  21. Ideal-Gas State Calculations — Pressure, volume, amount and Kelvin temperature
  22. Gas Mixtures and Dalton's Law — Mole fractions and partial pressures in one vessel
  23. Collecting Gas over Water — Subtracting water-vapour partial pressure
  24. Gas Density and Molar Mass — Deriving M = rho RT/P under ideal behaviour
  25. Mole Fractions after a Gas Reaction — Reaction extent followed by a new total gas amount
  26. Average Molar Mass of Gas Mixtures — Mole-weighted composition and density checks
  27. Gas Volumes at Different Conditions — Comparing PV/T values without an assumed molar volume
  28. Pressure Changes in a Rigid Reactor — Total gas moles at fixed volume and temperature
  29. Real-Gas Compressibility Calculations — Using Z = PV/nRT as a deviation measure
  30. Gas-Mixture Problem-Solving Review — Combining reaction, partial pressure and state equations
  31. Molarity, Molality and Mass Fraction Together — Keeping solution volume separate from solvent mass
  32. Density-Based Concentration Conversion — Choosing a one-litre solution basis
  33. Mixing Two Solutions of One Solute — Conserving solute moles before final-volume calculation
  34. Dilution with a Measured Final Volume — Applying c1V1 = c2V2 only when solute is conserved
  35. Mole Fraction in a Multicomponent Liquid — Including every component in the mole denominator
  36. Ideal Vapour Pressure of a Liquid Blend — Two Raoult-law partial pressures and their sum
  37. Vapour Composition from Partial Pressures — Calculating enrichment of the more volatile component
  38. Henry-Law Gas Solubility Problems — Using gas partial pressure and the stated constant convention
  39. Colligative Effect from Solute Mass — Converting grams through molality to a temperature shift
  40. Osmotic Pressure and Particle Factor — Linking analytical molarity to effective species
  41. Calorimetry Energy Balance — Heat gained and lost by solution, vessel and reaction
  42. Specific Heat and Temperature-Change Problems — Using q = mcDeltaT with units and signs
  43. Reaction Enthalpy per Mole of Extent — Scaling a measured heat to the balanced equation
  44. Enthalpy of Formation Cycles — Products minus reactants with stoichiometric coefficients
  45. Hess's Law by Equation Reversal — Changing equation direction, multipliers and enthalpy signs
  46. Combining Thermochemical Equations — Cancelling intermediates to reach a target reaction
  47. Bond-Enthalpy Estimates and Their Limits — Broken-minus-formed approximation for gas-phase bonds
  48. Kirchhoff-Type Heat-Capacity Corrections — Estimating reaction enthalpy at another temperature
  49. Entropy and Gibbs-Energy Calculations — Using DeltaG = DeltaH - TDeltaS with consistent units
  50. Thermochemical Cycle Problem-Solving Review — Reconciling calorimetry, formation data and state changes
  51. Equilibrium Constant from an ICE Table — Initial-change-equilibrium amounts and concentration units
  52. Reaction Quotient and Direction — Comparing Q with K before solving for equilibrium
  53. Gas Equilibrium with Changing Mole Number — Tracking partial pressures and reaction extent
  54. Kp and Kc Conversion — Using RT to the change in gas mole number
  55. Equilibrium Yield with a Limiting Feed — Separating maximum stoichiometric yield from equilibrium conversion
  56. Weak-Acid pH from an Equilibrium Table — Testing a small-ionisation approximation
  57. Buffer Ratio and Henderson–Hasselbalch — Converting moles after mixing before estimating pH
  58. Solubility Product and Ion Product — Testing precipitation with charge-correct stoichiometry
  59. Common-Ion Solubility Numericals — Distinguishing added-ion concentration from equilibrium solubility
  60. Equilibrium Numerical Review — Checking assumptions, roots and physical bounds
  61. Electrode Potentials and Cell Voltage — Cathode minus anode using reduction potentials
  62. Gibbs Energy and Cell Potential — Combining DeltaG = -nFE with reaction extent
  63. Nernst Equation Reaction Quotients — Concentration dependence with correct electron number
  64. Faraday-Law Deposition Calculations — Charge-to-electron moles and metal mass
  65. Conductivity and Molar Conductivity — Converting conductance with cell constant and concentration
  66. Rate from Concentration-Time Data — Stoichiometric normalisation of observed slopes
  67. Determining Reaction Orders from Trials — Initial-rate ratios that isolate one reactant
  68. Integrated First-Order Problems — Logarithms, half-life and elapsed time
  69. Arrhenius Two-Temperature Calculation — Solving activation energy from two rate constants
  70. Electrochemistry and Kinetics Numerical Review — Selecting electron, concentration and time bases
  71. Mixed Gas and Reaction Stoichiometry Challenge — Using limiting extent before partial pressures
  72. Mixed Solution and Equilibrium Challenge — Concentration conversion followed by reaction quotient
  73. Thermochemistry and Equilibrium Challenge — Relating heat, Gibbs energy and reaction direction
  74. Electrochemical Cell and Equilibrium Challenge — Cell potential linked to a nonstandard composition
  75. Kinetics and Temperature Challenge — Rate-law amount tracking with Arrhenius scaling
  76. Unknown Solute from Multiple Properties — Combining density, freezing shift and osmotic data
  77. Choosing Approximation versus Exact Algebra — Testing whether a simplification is numerically justified
  78. Physical Bounds and Alternative Solutions — Rejecting negative, over-complete or impossible roots
  79. Timed Problem-Solving Strategy — Prioritising givens, units and a final reasonableness check
  80. Physical Chemistry Problem Solving: Integrated Review — Conserving mass, charge and energy across quantitative topics