AQA 2024 AS CHEMISTRY 7404 EXAM/ QUALITY
DOCUMENT (physical chemistry) A+ GRADE,NEWEST
.
Enthalpy - CORRECT ANSWERS -The heat content that is stored in a chemical
system. q=mcDELTAt
Exothermic reactions - CORRECT ANSWERS -DeltaH is negative, gives out energy,
temperature decrease, forms bonds...
AQA 2024 AS CHEMISTRY 7404 EXAM/ QUALITY
DOCUMENT (physical chemistry) A+ GRADE,NEWEST
2024-2025.
Enthalpy - CORRECT ANSWERS -The heat content that is stored in a chemical
system. q=mcDELTAt
Exothermic reactions - CORRECT ANSWERS -DeltaH is negative, gives out energy,
temperature decrease, forms bonds e.g. oxidation... combustion of fuel, oxidation of
glucose carbohydrates
Endothermic reactions - CORRECT ANSWERS -DeltaH is positive, absorbs energy,
temperature increase, break bonds e.g. thermal decomposition, photosynthesis
Enthalpy change of a reaction - CORRECT ANSWERS -total energy absorbed - total
energy released
Mean bond enthalpy - CORRECT ANSWERS -The average value of the bond
dissociation enthalpy for a given type of bond taken from a range of different
compounds.
Calorimetry - CORRECT ANSWERS -An experimental procedure used to measure the
energy transferred from one substance to another as heat.
Titration - CORRECT ANSWERS -a method to determine the concentration of a
substance in solution by adding a solution of known volume and concentration until the
reaction is completed, which is usually indicated by a change in colour.
Ionic equation - CORRECT ANSWERS -details of reactions that involve ions in an
aqueous solution
Balanced equation - CORRECT ANSWERS -a chemical equation in which mass is
conserved; each side of the equation has the same number of atoms of each element
Ionisation energy group 2 - CORRECT ANSWERS -Ionisation energy decreases as you
go down group 2, as the outermost electrons are held in additional shells further from
the nucleus, the outer electrons are shielded from the nucleus and nuclear attraction is
greatly reduced.
Ionisation energy period 3 - CORRECT ANSWERS -Increases due to increasing
protons so stronger nuclear attraction, no effect from shielding. Drop between group 2
and 3 shows sub-shell structure. Drop between 5 and 6 is due to electron repulsion.
Factors affecting ionisation energy - CORRECT ANSWERS -Greater nuclear charge =
higher IE, Closer (outer electron) to the nucleus = higher IE, Less shielding = higher IE.
, Sub shells - CORRECT ANSWERS -Shells are divided into sub-shells which are made
up of orbitals, S P D F
Hess's law - CORRECT ANSWERS -The total enthalpy change of a reaction is
independent of the route taken.
Mass number - CORRECT ANSWERS -Total number of protons and neutrons.
Atomic number - CORRECT ANSWERS -Numbers of protons in the nucleus and
number of electrons in shells.
Negative Ions - CORRECT ANSWERS -More electrons than protons.
Positive ions - CORRECT ANSWERS -More protons than electrons.
Relative isotopic mass - CORRECT ANSWERS -mass of an atom of an isotope of an
element on a scale where an atom of carbon12 is 12.
Relative atomic mass - CORRECT ANSWERS -average mass of an atom of an element
on a scale where an atom of carbon12 is 12.
Relative molecular mass - CORRECT ANSWERS -average mass of a molecule on a
scale where an atom of carbon12 is 12.
First ionisation energy - CORRECT ANSWERS -the energy needed too remove 1
electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
Second ionisation energy - CORRECT ANSWERS -the energy needed to remove 1
electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.
Number of particles= - CORRECT ANSWERS -Number of moles x Avagadros constant
(6.02 x 10^23)
Number of moles= - CORRECT ANSWERS -Mass / Mr
Number of moles= - CORRECT ANSWERS -Concentration (moldm^-3) x Volume
(dm^3)
Methyl orange indicator - CORRECT ANSWERS -yellow in acid, red in alkali.
Commonly used in titrations.
Phenolphthalein indicator - CORRECT ANSWERS -pink in alkali, colourless in acid.
Commonly used in titrations.
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