IB Chemistry SL flashcards
IB Chemistry SL · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Mole
- One mole contains 6.02 × 10^23 specified entities. Amount in moles equals number of entities divided by Avogadro constant, linking mass and molar mass.
- Empirical formula
- The simplest whole-number ratio of atoms of each element in a compound; molecular formula is a whole-number multiple of it.
- Relative atomic mass
- The weighted mean mass of an atom of an element compared with one-twelfth the mass of a carbon-12 atom, accounting for isotope abundances.
- Ideal gas equation
- PV = nRT relates pressure, volume, amount and absolute temperature; use pascals, cubic metres, kelvin and R = 8.314 J K−1 mol−1.
- First ionisation energy
- Energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
- VSEPR theory
- Electron domains around a central atom repel and arrange as far apart as possible; lone pairs repel more strongly than bonding pairs, reducing bond angles.
- Hydrogen bond
- A strong intermolecular attraction between a hydrogen atom bonded to N, O or F and a lone pair on N, O or F in another molecule.
- Metallic bond
- Electrostatic attraction between a lattice of positive metal ions and delocalised electrons; explains electrical conductivity and malleability.
- Bond enthalpy
- Enthalpy change when one mole of a specified bond is broken in gaseous molecules; mean values estimate reaction enthalpy from bonds broken minus bonds formed.
- Giant covalent structure
- A three-dimensional network of atoms joined by covalent bonds, such as diamond or silicon dioxide, giving high melting points and hardness.
- Alkali metals
- Group 1 elements with one valence electron; they form 1+ ions and become more reactive down the group as ionisation energy decreases.
- Halogen displacement
- A more reactive halogen oxidises and displaces a less reactive halide ion from solution; reactivity decreases down Group 17.
- Homologous series
- A family of organic compounds with the same functional group and general formula, showing gradual change in physical properties and similar reactions.
- Amphoteric oxide
- An oxide that can react with both acids and bases to form salts, for example aluminium oxide and zinc oxide.
- Exothermic reaction
- A reaction that releases energy to the surroundings, giving a negative enthalpy change because products have lower enthalpy than reactants.
- Hess's law
- The enthalpy change of a reaction is independent of route; it equals the sum of enthalpy changes for any sequence converting reactants to products.
- Entropy
- A measure of dispersal of energy or disorder; it generally increases from solid to liquid to gas and when more particles form.
- Gibbs free energy
- ΔG = ΔH − TΔS; a negative ΔG indicates a spontaneous change at constant temperature and pressure.
- Standard enthalpy of formation
- Enthalpy change when one mole of a compound forms from its elements in their standard states under standard conditions.
- Collision theory
- Particles react only when they collide with sufficient energy and correct orientation; higher temperature, concentration or surface area increases successful collisions.
- Dynamic equilibrium
- Forward and reverse reaction rates are equal in a closed system, so concentrations remain constant although both reactions continue.
- Equilibrium constant Kc
- For aA + bB ⇌ cC + dD, Kc = [C]^c[D]^d/([A]^a[B]^b); it changes only with temperature, not concentration or pressure.
- Le Chatelier's principle
- When a system at equilibrium is disturbed, it shifts in the direction that opposes the change; changes in concentration, pressure or temperature can cause shifts.
- Percentage yield
- Actual amount of product obtained divided by theoretical maximum amount, multiplied by 100; measures reaction efficiency.
- Brønsted–Lowry acid
- A proton donor; its conjugate base forms after it loses H+, and together they differ by one hydrogen ion.
- pH
- pH = −log10[H+], where [H+] is hydrogen ion concentration in mol dm−3; acidic solutions have pH below 7 at 298 K.
- Oxidising agent
- A species that accepts electrons and is itself reduced; it causes another species to be oxidised.
- Electrochemical cell
- A device converting chemical energy to electrical energy; oxidation occurs at the anode and reduction at the cathode, giving a positive cell potential when spontaneous.
- Independent variable
- The factor deliberately changed by the investigator while other relevant variables are controlled, allowing its effect on the dependent variable to be tested.
- Systematic error
- A consistent error that shifts measurements in the same direction, often from faulty calibration or method; it reduces accuracy rather than precision.
- Percentage uncertainty
- Absolute uncertainty divided by the measured value, multiplied by 100; for multiplication or division, percentage uncertainties are added.
- Rf value
- In chromatography, the distance travelled by a spot divided by the distance travelled by the solvent front, measured from the same origin.