Studied by 5 people
Relative Atomic Masses Ar
weighted average of the masses of the isotopes in a naturally occurring sample of the element relative to 1/12 of the mass of a carbon 12 atom
First ionisation energy
The energy required to remove one mole of electrons from one mole of isolated gaseous atoms
Relative isotopic mass Ir |
The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12
Relative molecular mass Mr
the mass of that molecule compared to 1/12 the relative atomic mass of an atom of carbon-12
Avogadro’s constant
the number of atoms in 12g of carbon-12
Mole
The amount of substance that contains as many particles as there are in 12g of carbon-12
Empirical formula
The simplest whole number ratio of the atoms of each element present
Molecular formula
The actual number of atoms of each element in one molecule of the compound
Ideal gas
A gas composed of identical particles in continuous, random motion. The particles are considered point like. Collisions are elastic and do not result in reaction. |
Boyle’s Law
At constant temperature T, the volume V, of a fixed gas is inversely proportional to the pressure, p, applied to it |
Ideal gas law
Equal volumes of all gases at the same pressure and temperature contain the same number of particles
VESPR theory
Charge clouds in valence shell of an atom repel each other and this forces the pairs of electrons to move themselves as far as possible to minimise repulsion.
Electronegativity
Electronegativity is the power of an atom (relative ability) to attract the bonding pair of electrons in a covalent bond to itself.
Hydrogen bonds
The hydrogen bond is the force of attraction between the lone pair of electrons on the neighbouring electronegative atom and the δ+ charge on the hydrogen atoms. |
Temperature
A measure of the average kinetic energy of particles
Heat
Heat is the form of energy that flows from something at a higher temperature to something at a lower temperature
Enthalpy change
heat change of a reaction measured under conditions of constant pressure.
Standard enthalpy of combustion ΔHcꝊ
The enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions, all reactants and products being in their standard states.
Standard enthalpy of formation ΔHfꝊ
The enthalpy change when 1 mole of a substance is formed from its constituent elements under standard conditions, all reactants and products being in their standard states.
Standard enthalpy change of reaction ΔHrꝊ
The enthalpy change when molar amounts of reactants, as shown in the stoichiometric equation, react together under standard conditions.
Enthalpy change of neutralisation ΔHneutꝊ
The enthalpy change when one mole of water molecules is formed when and acid (H+) reacts with an alkali (OH-) under standard conditions |
Enthalpy change of solution
The enthalpy change when one mole of solute is dissolved in excess solvent to form a solution of ‘infinite dilution’ under standard conditions |
Specific heat capacity
The energy required to raise the temperatures of 1g of substances by 1K, measures inJg-1K-1
First law of thermodynamics
The enthalpy change accompanying a chemical reaction is independent of the pathway between the initial and final states |
Mean bond enthalpy
The average amount of energy required to break one mole of a particular type of covalent bond in a gaseous molecule averaged over a range of similar compounds |
Structural isomers
Molecules with the same molecular formula but a different structural formula
Homologous series
A homologous series is a group of compounds of the same functional group with the same general formula
Functional group
An atom or group of atoms that is typical fro a particular organic family and gives rise to its chemical properties
General formula
The general formula is an algebraic formula which can describe members of a homologous series
Nucleophile
An electron pair donor
Elimination
Removal of an atom/group of atoms from a parent molecule
Geometric isomers
All atoms are connected to each other in the same way and have the same molecular formula ,however the atoms are arranged differently in space
Homolytic fission
When a covalent bond is broken equally such that each atom in the bond accepts one electron
Heterolytic fission
When a covalent bond is broken unequally so that an atom in the bond receives both electrons to become an anion, the other a cation
Monomer
A small reactive molecule that contains the smallest group of atoms repeated throughout the chain (basic unit of a polymer)
Oxidising agent
A substance which oxidises another atom / molecule by gaining electrons (being reduced) causing other substances to lose electrons and be oxidised |
Reducing agent
A substance which reduces another atom / molecule by losing electrons (being reduced) causing other substances to gain electrons and be reduced
Structural isomer
A structural isomer is a molecule that has the same molecular formula but different structural formulas
Position isomer
Position isomers are structural isomers which have different structural formula due to the functional group being in a different place along the chain
Functional group isomer
Functional group isomers have the same molecular formula but a different structural formula due to having different functional groups
Electron-releasing groups
(CH3, OCH3, NH2) Releases electrons onto the benzene ring and hence increases the electron density on the ring, hence the electrophile is more strongly attracted and so the reaction is much faster (direct further substitution to the 2,4 and 6 positions.
Electron withdrawing groups
(NO2, COCl) These withdraw electrons from the ring making it less susceptible to further electrophilic substitutions (encourage substitutions on 3 and 5 positions)
Catalysts
A catalyst speeds up the rate of reaction without getting used u in the process. It does this by providing an alternate reaction pathway with a lower activation energy
Heterogenous catalyst
A heterogeneous catalyst is in a different phase from the reactants
Homogenous catalyst
A homogeneous catalyst is in the same phase as the reactant
Activation energy
The minimum energy needed for a successful collision
Rate of reaction
Measured change in concentration of reactant or product in time
Rate determining step
The rate of the slowest step which will govern the rate of the reaction
Equivalence point
The volume at which exactly the same number of moles of hydrogen ions and hydroxide ions have been added
End -point
The volume of acid or alkali added so that the indicator just changes colour
Buffers
Buffers are solutions that resist changes in pH when small amounts of acid or alkali are added to them (maintains a constant pH, despite dilution or addition of small amounts of acid or base
Relative mass of an electron
1/1840
Principle quantum number
The number of energy levels/shells
How many electrons can fit in each shell in ascending order
2, 8, 18, 32
What are sub shells?
principal quantum shells are split into subshells, s, p, d and f they contain multiple orbitals, which exist at specific energy levels and can contain up to 2 electrons. The s subshells has 1 orbital, p has 3, d has 5 and f has 7.
What are the exceptions in ionisation energy in?
Between Beryllium and Boron (and Mg and Al) there is decrease in ionisation energy. And between Nitrogen and Oxygen (and P and S) there is a decrease in ionisation energy.
What is the reason for the exceptions in ionisation energy between Be/B and Mg/Al?
5th electron in B/13th electron in Al are in the 2p/3p subshells which is further from the nucleus than the 2s/3s subshells. Hence lower effective nuclear charge and it takes less energy to remove the electron.
What is the reason for the exceptions in ionisation energy between N/O and P/S?
In N/P all the electrons in the 2p/3p subshells are unpaired while in O/S there is on orbital with paired electrons. SInce there electrons are both negative they will repel each other which will make it easier for one of these electrons to be removed.
2 bonding pairs and 0 lone pairs
Linear 180°
2 bonding pairs 2 lone pairs
V- shaped 104.5° (water)
3 bonding pairs 0 lone pairs
Trigonal planar 120°
3 bonding pairs 1 lone pair
Trigonal pyramidal 107°
4 bonding pairs 0 lone pairs
Tetrahedral 109.5°
5 bonding pairs 0 lone pairs
Trigonal bipyramidal 90° and 120°
6 bonding pairs 0 lone pairs
90°
What is a permanent dipole?
Two atoms that are bonded have different electronegativities the more elctronegative atom draws more of the negative charge towards itself producing a δ+ and δ- atom.
What is an induced dipole?
A δ+ /δ- is created due to proximity with a different charged particle.
Bond breaking is…
endothermic
Bond making is …
exothermic
What is Hess’s law?
the energy change that occurs when a reaction takes place is the same, regardless of the route taken
What are the properties of chemical equilibria?
rate of the forwards and backwards reaction are the same
the concentrations of reactants and products are constant
What is a closed system?
When none of the reactants or products can escape the reaction mixture. (however energy can)
What is an open system?
Matter and energy can be lost to the surroundings
What is an isolated system?
No matter or energy can escape to the surroundings
Lewis acid
electron pair acceptor
Lewis base
electron pair donor
Bronsted-Lowry acid
proton donor
Bronsted Lowry base
proton acceptor
sodium potassium and ammonium compounds
soluble
nitrates
soluble
chlorides except silver and lead(II)
soluble
silver and lead(II) chlorides
insoluble
sulfates except barium calcium and lead(II)
soluble
barium calcium and lead(II) sulfates
insoluble
Sodium potassium and ammonium carbonates
soluble
carbonates except sodium potassium and ammonium
insoluble
sodium potassium and calcium hydroxides
soluble
hydroxides except for sodium potassium and calcium
insoluble
ionisation enthalpy
the amount of energy required to remove an electron from a gaseous atom of an element to form a gaseous ion under standard conditions
electron affinity
the energy change when one mole of electrons is gained by one mole of gaseous atoms of an element to form one mole of gaseous ions under standard conditions
the enthalpy change when 1 mole of gaseous atoms is formed from its element under standard conditions
Entropy (S)
a measure of how disordered or chaotic a system is
What causes an increase in entropy?
more gaseous products
more aqeous/liquid products
a greater number of moles of products
Spontanous
a reaction that will take place of its own accord / is energetically favourable under standard conditions.
Feasible
a reaction that will of its own accord / is energetically favourable however may not necessarily take place at a high enough rate under standard conditions.
ΔHrꝋ<0 and ΔSꝋ>0
ΔGꝋ<0 and spontaneous (forward reaction spontaneous at any T)
ΔHrꝋ>0 and ΔSꝋ<0
ΔGꝋ>0 never takes place (backwards reaction spontaneous at and T)
ΔHrꝋ<0 and ΔSꝋ<0
ΔGꝋ<0 at low T >0 at high T (only spontaneous at low T)
ΔHrꝋ>0 and ΔSꝋ>0
ΔGꝋ<0 at high T >0 at low T (only spontaneous at high T)
Note 
Flashcard (59)