module 3/5 Flashcards
What is periodicity?
a repeated trend in properties of elements across periods in the periodic table
Define ‘First Ionisation Energy’
Give an example
to remove 1 mole of electrons from 1 mole of gaseous atoms (to form 1 mole of gaseous 1+ ions) e.g. Mg(g) → Mg+(g) + e–
Define ‘Average Bond Enthalpy’
Give an example
The enthalpy required to break 1 mole of covalent bonds in the gaseous state e.g. ¼ CH4(g) → ¼ C(g) + H(g)
Define ‘ Enthalpy of formation’
The enthalpy required to make 1 mole of compound from elements e.g. Mg(s) + ½ O2(g) →MgO(s)
Define ‘Enthalpy of combustion’
The enthalpy change required to react 1 mole of a substance fully with oxygen / in excess oxygen e.g. CH3OH(g) + 1½ O2(g) - CO2(g) + 2 H2O(l)
Define ‘Neutralisation Enthalpy’
The enthalpy change required to form 1 mole of water when acid and alkali/base react e.g. HCl(aq) + NaOH(aq) à NaCl(aq) + H2O(l) or H+(aq) + OH–(aq) à H2O(l)
What are the ‘standard state conditions’?
298 K / 25 oC 1 atm / 100 kPa / 100,000 Pa all solutions 1.0 mol dm-3
Define ‘Lattice Enthalpy’
The enthalpy change required to form 1 mole of an ionic lattice from ions in the gaseous state e.g. Mg2+(g) + 2 Cl–(g) -> MgCl2(s)
Define ‘ Atomisation’
to form 1 mole of gaseous atoms from its element e.g. Mg(s) -> Mg(g)
Define ‘First Electron Affinity’
to form 1 mole of gaseous 1- ions from 1 mole of gaseous atoms (by adding 1 mole of electrons) e.g. Cl(g) + e– -> Cl–(g)
Define ‘solution Enthalpy’
The enthalpy change required to dissolve 1 mole of a substance in excess water e.g. MgCl2(s) -> MgCl2(aq)
Define ‘ Hydration Enthalpy’
The enthalpy change required to change 1 mole of gaseous ions into 1 mole of aqueous ions e.g. Mg2+(g) -> Mg2+(aq)
Define ‘Entropy’
the disorder within a substance / system
Define ‘Activation energy’
minimum energy needed by particles to react
Define ‘Catalyst’
speeds up a chemical reaction not used up, / is regenerated in the reaction, provides an alternative pathway for the reaction to proceed, provides a different lower activation energy Ec.
Define ‘Hetreogenous’
in different states
Define ‘Homogenous’
in the same state
Define ‘Half-life’
the time is takes for the concentration of a reactant to halve
Define ‘Rate-determining step’
the slowest step in a multi-step mechanism
Define ‘Dynamic Equilbrium’
forward and back reaction occur at the same rate concentrations of reactants/products do not change closed system
Define ‘Acid’
proton donor
Define ‘Base’
proton acceptor
Define ‘Alkali’
soluble base (produces OH–(aq))
Define ‘Strong Acid’
fully dissociates in solution e.g. HNO3(aq) -> H+(aq) + NO3–(aq) (has no Ka / pKa value)
Define ‘weak acid’
partially dissociates in solution e.g. HNO2(aq) ->(
<-)H+(aq) + NO2–(aq) (has a Ka / pKa value)
Define ‘ Conjugate acid-base pair’
differ by just one H+ ion
e.g. conjugate acid: CH3COOH
conjugate base: CH3COO–
Define ‘ Conjugate Acid’
donates a proton to form its conjugate base
Define ‘conjugate base’
accepts a proton to form its conjugate acid
Define ‘monobasic acid’
donates/dissociates one H+ per molecule
Define ‘salt’
where an acid has an H+ ion replaced by a metal or ammonium ion
Define ‘neutral’
[H+] = [OH–]
Define ‘Buffer’
minimises the change in pH when small quantities of acid or alkali are added
Define ‘End Point (of a titration)’
the indicator changes colour and we stop adding any more titrant
Define ‘Equivalence point (of a titration)’
the volume/amount of acid/alkali added has reacted exactly with the alkali/acid
Define ‘Vertical Section’
shows a rapid change in pH contains the equivalence point contains the end point if the right indicator is chosen
Define ‘Indicator’
a weak acid that changes colour at different pH
Define ‘Electrode potential’
the voltage of a half-cell when connected to a standard hydrogen electrode
Define ‘d-block element’
an atom whose highest energy electron is in a d-orbital / d-subshell
Define ‘Transition metal’
an element that can form a stable ion with an incomplete d-subshell
Define ‘ complex ion’
Transition metal ion with coordinate bonds to ligands
Define ‘Ligand’
species with a lone pair that can form a coordinate bond with a transition metal ion
Define ‘Bidenate Ligand’
species with two lone pairs that can form two coordinate bonds with a transition metal ion
Define ‘Coordinate Bond’
formed when a ligand shares a pair of electrons with a transition metal ion
Define ‘coordiantion number’
total number of coordinate bonds in a complex formed between the ligand(s) and the transition metal ion (typically 4 or 6)
