Bulgaria DZI Chemistry flashcards
Bulgaria DZI Chemistry · Build recall with a focused review session.
34 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Atomic number
- The number of protons in the nucleus of an atom; it defines the element and, in a neutral atom, equals the number of electrons.
- Isotopes
- Atoms of the same element with identical proton numbers but different neutron numbers, so they differ in mass number while sharing chemical properties.
- Hund's rule
- Within a set of degenerate orbitals, electrons occupy separate orbitals with parallel spins before any orbital receives a second electron, minimising repulsion.
- First ionisation energy
- The energy required to remove one mole of electrons from one mole of gaseous atoms to form gaseous 1+ ions; it rises across a period.
- Electronegativity
- The tendency of an atom in a bond to attract the shared electron pair toward itself; it increases across a period and decreases down a group.
- Hydrogen bonding
- A strong intermolecular attraction between a hydrogen atom bonded to N, O or F and a lone pair on a nearby electronegative atom.
- VSEPR theory
- Electron pairs around a central atom arrange themselves as far apart as possible; lone pairs repel more strongly than bonding pairs, shrinking bond angles.
- Mole concept
- One mole contains Avogadro's number (6.02 × 10²³) of particles and equals the amount whose mass in grams is the relative molecular mass.
- Molar volume of gas
- At standard temperature and pressure, one mole of any ideal gas occupies 22.4 litres, allowing conversion between amount and volume.
- Limiting reagent
- The reactant that is completely consumed first, determined by dividing each amount by its stoichiometric coefficient; it fixes the maximum product yield.
- Percentage yield
- The actual mass of product obtained divided by the theoretical mass calculated from stoichiometry, multiplied by one hundred.
- Strong electrolyte
- A substance that dissociates almost completely into ions in aqueous solution, giving high conductivity, such as sodium chloride or hydrochloric acid.
- pH scale
- The negative logarithm of the hydrogen ion concentration; values below seven are acidic, seven is neutral and above seven is basic at 25 °C.
- Solubility product Ksp
- The equilibrium constant for dissolution of a sparingly soluble salt; precipitation occurs when the ion product exceeds this constant.
- Neutralisation
- The reaction of an acid with a base to form a salt and water, in which hydrogen ions and hydroxide ions combine in equal amounts.
- Displacement in halogens
- A more reactive halogen displaces a less reactive halide from solution; the order of oxidising strength is chlorine, bromine, iodine.
- Ammonia as a base
- Ammonia accepts a proton from water to form ammonium and hydroxide ions, making its aqueous solution weakly basic.
- Carbon dioxide test
- Carbon dioxide turns limewater milky by precipitating calcium carbonate, and the precipitate dissolves when excess carbon dioxide forms bicarbonate.
- Activity series
- A ranking of metals by reactivity; metals above hydrogen displace it from dilute acids, while those below do not react.
- Amphoteric hydroxide
- A hydroxide such as aluminium or zinc hydroxide that dissolves in both acid and alkali because it can act as acid or base.
- Thermal decomposition of carbonate
- Heating a carbonate, such as calcium carbonate, breaks it down into the metal oxide and carbon dioxide gas.
- Rusting of iron
- Corrosion requiring both oxygen and water, producing hydrated iron oxide; zinc coating protects iron by oxidising preferentially.
- Markovnikov's rule
- When hydrogen halide adds to an unsymmetrical alkene, the hydrogen atom attaches to the carbon already bearing the greater number of hydrogen atoms.
- Addition polymerisation
- Monomers containing carbon-carbon double bonds join without loss of atoms, forming a long saturated chain such as polyethene from ethene.
- Benzene aromaticity
- Benzene is a planar ring of six carbons with delocalised pi electrons, giving extra stability and a preference for substitution over addition.
- Geometric isomerism
- Cis-trans isomers arise when restricted rotation about a double bond places identical groups on the same side or opposite sides.
- Tollens' reagent test
- A silver ammonia complex that aldehydes reduce to metallic silver, giving a mirror; ketones give no reaction.
- Esterification
- A carboxylic acid reacts with an alcohol in the presence of an acid catalyst to form an ester and water in a reversible reaction.
- Amine basicity
- Amines are basic because the nitrogen lone pair accepts a proton; alkyl groups increase basicity in water by donating electron density.
- Peptide bond
- The amide link formed between the carboxyl group of one amino acid and the amino group of another, releasing water and building proteins.
- Hess's law
- The enthalpy change of a reaction is independent of the route taken, so enthalpies of individual steps may be summed to find the overall value.
- Activation energy
- The minimum energy colliding particles must possess for a reaction to occur; a catalyst lowers it without altering the enthalpy change.
- Le Chatelier's principle
- When a system at equilibrium is disturbed, it shifts in the direction that partially opposes the change in concentration, pressure or temperature.
- Equilibrium constant K
- The ratio of product concentrations raised to their coefficients to reactant concentrations raised to theirs at equilibrium; it depends only on temperature.