ICO Part B (ORI) flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Flash point

The lowest temperature at which a liquid's vapour can ignite momentarily in air. Used to classify flammable liquids; lower flash point means higher fire risk.

Peroxide formers

Ethers such as diethyl ether and THF slowly form explosive peroxides on storage. Test with KI/starch or commercial strips before distillation; store over KOH or under argon.

Fume hood face velocity

Typical safe range is 0.3–0.5 m/s (80–100 fpm). Too low allows vapour escape; too high causes turbulence and loss of containment.

GHS pictograms

Nine hazard symbols: flame, flame over circle, exploding bomb, gas cylinder, corrosion, skull and crossbones, health hazard, exclamation mark, environment. Each indicates a specific hazard class.

Spin-only magnetic moment

μ = √(n(n+2)) Bohr magnetons, where n is the number of unpaired electrons. Compare with measured magnetic moment to infer spin state and geometry of a complex.

Spectrochemical series

Ligand field strength order: I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H2O < NH3 < en < NO2⁻ < CN⁻ ≈ CO. Strong-field ligands cause large Δo and low-spin complexes.

High-spin vs low-spin

If Δo > pairing energy, electrons pair in lower orbitals (low-spin). If Δo < pairing energy, electrons occupy higher orbitals (high-spin). 4d/5d metals are usually low-spin.

Jahn–Teller distortion

Tetragonal elongation in octahedral complexes with degenerate ground-state electron configurations, notably d9 (Cu2+) and high-spin d4 (Cr2+, Mn3+).

Molar conductance

Λm = κ/c, where κ is conductivity and c is concentration. A 1:1 electrolyte in water typically gives ~100–150 S cm² mol⁻¹, helping determine ionisation type.

Retrosynthetic analysis

Breaking a target molecule into simpler precursors (synthons) by reversing bond-forming reactions. Guides selection of reagents and protecting groups.

Rf value

Retention factor in thin-layer chromatography: Rf = distance travelled by spot / distance travelled by solvent front. Characteristic of a compound in a given solvent system.

Eluotropic series

Solvent strength order on silica: hexane < toluene < dichloromethane < ethyl acetate < acetone < methanol < water. Used to choose mobile phase for column chromatography.

PCC oxidation

Pyridinium chlorochromate is a mild oxidant that converts primary alcohols to aldehydes (not carboxylic acids) and secondary alcohols to ketones, in dichloromethane.

Mixed melting point

If a mixture of two samples melts at the same temperature as the pure compound, they are identical. A depression indicates different compounds.

Primary standard

A highly pure, stable, non-hygroscopic reagent used to standardise a titrant. Examples: KHP for bases, Na2CO3 for acids, K2Cr2O7 for redox titrations.

Beer–Lambert law

A = εbc, where A is absorbance, ε is molar absorptivity, b is path length, and c is concentration. Linear at low concentration; deviations occur at high concentration.

EDTA titration

EDTA forms 1:1 complexes with most metal ions. Buffer to pH 10 for Ca2+/Mg2+ and use Eriochrome Black T indicator; endpoint is colour change from wine-red to blue.

Gravimetric factor

Mass of analyte = mass of precipitate × (molar mass analyte / molar mass precipitate). Example: BaSO4 for sulfate, AgCl for chloride.

Acid–base indicator choice

Choose an indicator whose pKa is close to the equivalence pH. Phenolphthalein (8.2–10.0) for weak acid–strong base; methyl orange (3.1–4.4) for strong acid–weak base.

Arrhenius equation

k = A exp(-Ea/RT). A plot of ln k versus 1/T gives a straight line with slope -Ea/R, allowing determination of activation energy.

First-order half-life

t1/2 = ln2/k ≈ 0.693/k. Independent of initial concentration. For second-order, t1/2 = 1/(k[A]0).

Nernst equation

E = E° - (RT/nF) ln Q. At 298 K, E = E° - (0.0592/n) log Q. Relates cell potential to reaction quotient and concentrations.

Gibbs free energy relation

ΔG = ΔH - TΔS. Also ΔG° = -RT ln K and ΔG° = -nFE°cell. Negative ΔG indicates spontaneous reaction under stated conditions.

Calorimetry

q = mcΔT. Bomb calorimetry measures ΔU at constant volume; enthalpy ΔH = ΔU + ΔnRT for reactions involving gases.

Kohlrausch law

Λm = Λ°m - K√c for strong electrolytes. Extrapolation to zero concentration gives limiting molar conductivity Λ°m.

Systematic vs random error

Systematic (determinate) error shifts results consistently, affecting accuracy; random (indeterminate) error varies unpredictably, affecting precision. Gross errors are blunders.

Standard deviation

s = √[Σ(xi - x̄)²/(n-1)]. Measures precision. Relative standard deviation (RSD) = (s/x̄) × 100%.

Confidence interval

x̄ ± t(s/√n), where t is from Student's t-table for n-1 degrees of freedom and the chosen confidence level (e.g., 95%).

Uncertainty propagation

For addition/subtraction, absolute uncertainties add in quadrature: σ² = σa² + σb². For multiplication/division, relative uncertainties add in quadrature.

Degrees of unsaturation

DBE = C - H/2 + N/2 + 1 (halogens count as H). Each DBE corresponds to a ring or π bond; helps deduce structure from molecular formula.

IR carbonyl stretch

C=O stretching appears at 1650–1750 cm⁻¹. Conjugation lowers frequency; ring strain raises it. Useful for identifying aldehydes, ketones, esters, and amides.

1H NMR integration

The area under each signal is proportional to the number of equivalent protons. Multiplicity follows the n+1 rule for first-order spectra; coupling constants J are in Hz.

Molecular ion in mass spectrometry

The peak corresponding to the intact molecule (M+). Its m/z gives molecular mass; isotope patterns (M+2 for Cl, Br) reveal halogen content.