2025 AQA AS CHEMISTRY Paper 2
Organic and Physical Chemistry
Question Paper & Mark Scheme
(Merged)
Describe the nuclear model of an atom. [2] -answers - Nucleus containing of protons
and neutrons.
- Surrounded by electrons in energy levels.
State the relative mass and charges of a proton [2]. -answers Mass: 1
Charge: +1
State the relative mass and charges of a neutron. [2] -answers Mass: 1
Charge: 0
Define atomic number (Z). [1] -answers The number of protons in an atom.
State the relative mass and charges of an electron. [2] -answers Mass: 1/1840
Charge: -1
Define mass number (A). [1] -answers The number of protons and neutrons combined
in an atom
Define isotope. [1] -answers Atoms with the same number of protons but a different
number of neutrons.
Describe the chemical properties of two isotopes of the same element. [2] -answers -
Same chemical properties.
-As same electron configuration.
State the uses of mass spectrometry: [4] -answers - Identify elements
- Determine relative molecular mass.
- Determine isotopic mass.
- Determine relative abundance of isotopes.
Why is mass spectrometry done in a vacuum? [1] -answers Prevent positive ions from
colliding with molecules in the air.
,Describe electrospray ionisation: [4] -answers - Sample dissolved in volatile solvent.
- Injected through a fine hypodermic needle giving a fine mist/aerosol.
- Tip of needle connected to positive terminal of a high voltage.
- Each molecule gains a proton as it leaves the needle.
Describe acceleration: [2] -answers - The positive ions are attracted to a negatively
charged plate and accelerate towards it.
- All ions accelerate forward so that they have the same kinetic energy, but reach
different velocities due to their varying masses. (lighter → faster)
Describe ion drift: [2] -answers - Some of the ions pass through a hole in the negatively
charged plate, forming a beam of particles. They travel along the 'flight tube' towards
the detector.
- As the ions are travelling at different speeds, they drift apart further.
Describe detection: [2] -answers - When the positive ions hit the negatively charged
detection plate, they gain an electron.
- This generates a current, the size of which is proportional to the number of each type
of ion.
Describe data analysis: [1] -answers The signal from the detector is passed to a
computer which generates a mass spectrum from the current.
What does each peak on the graph represent? [2] -answers - Each peak represents
different isotope.
- Height gives relative abundance of each isotope.
Give the formula for relative atomic mass: [1] -answers (sum of abundances not 100)
Describe where electrons are found. [3] -answers - Found in shells, orbiting nucleus.
- Within each shell there are sub-shells.
- Within each sub-shell we find orbitals.
Define orbital. [1] -answers An orbital is a region within an atom that can hold up to two
electrons with opposite spins.
How many orbitals are there in...
a) an s sub-shell
b) a p sub-shell
c) a d sub-shell [3] -answers a) one s orbital
b) three p orbitals
c) five d orbitals
Define highest energy electron. [1] -answers The outer most electron on an atom or ion.
, What is stated by the Aufbau principle? [1] -answers Orbitals of lower energy are always
filled first.
What are the exceptions to the Aufbau principle? [3] -answers Cr - 3d5 4s2
Cu - 3d10 4s1
Define ionisation energy. [2] -answers The amount of energy needed to remove a mole
of electrons from a mole of atoms, in the gaseous state.
Units kJmol-1
Why does ionisation energy increase each time? [1] -answers The second electron is
removed from an ion that already has a positive charge.
Give the equation for 3rd ionisation energy. [1] -answers
State 3 factors affecting ionisation energy: [3] -answers - Atomic Radius
- Nuclear Charge
- Shielding
Explain how atomic radius affects ionisation energy. [2] -answers - How far the outer
electrons are from the attractive power of the nucleus.
- The further an outer electron from the attractive power of the nucleus, the less energy
is required to ionise it.
Explain how nuclear charge affects ionisation energy. [2] -answers - How many protons
are attracting the outer electron.
- The greater the nuclear charge, the stronger the attraction to the outer electron, so
more energy is required to ionise it.
Explain how shielding affects ionisation energy. [2] -answers - How many electrons are
between the nucleus and the outer electron so shielding the attractive power of the
nucleus.
- The more inner electrons there are, the more the nucleus is shielded and the less
energy is required to ionise the outer electron.
Explain the trend in ionisation energy down a group [3] -answers Ionisation energy
decreases going down the group.
- Atomic radius increases
- More shielding
Explain the general trend in ionisation energy across Period 3. [3] -answers General
increase in IE across Period 3, this is because...
- Across the period there is a greater nuclear charge.
- Same amount of shielding
Organic and Physical Chemistry
Question Paper & Mark Scheme
(Merged)
Describe the nuclear model of an atom. [2] -answers - Nucleus containing of protons
and neutrons.
- Surrounded by electrons in energy levels.
State the relative mass and charges of a proton [2]. -answers Mass: 1
Charge: +1
State the relative mass and charges of a neutron. [2] -answers Mass: 1
Charge: 0
Define atomic number (Z). [1] -answers The number of protons in an atom.
State the relative mass and charges of an electron. [2] -answers Mass: 1/1840
Charge: -1
Define mass number (A). [1] -answers The number of protons and neutrons combined
in an atom
Define isotope. [1] -answers Atoms with the same number of protons but a different
number of neutrons.
Describe the chemical properties of two isotopes of the same element. [2] -answers -
Same chemical properties.
-As same electron configuration.
State the uses of mass spectrometry: [4] -answers - Identify elements
- Determine relative molecular mass.
- Determine isotopic mass.
- Determine relative abundance of isotopes.
Why is mass spectrometry done in a vacuum? [1] -answers Prevent positive ions from
colliding with molecules in the air.
,Describe electrospray ionisation: [4] -answers - Sample dissolved in volatile solvent.
- Injected through a fine hypodermic needle giving a fine mist/aerosol.
- Tip of needle connected to positive terminal of a high voltage.
- Each molecule gains a proton as it leaves the needle.
Describe acceleration: [2] -answers - The positive ions are attracted to a negatively
charged plate and accelerate towards it.
- All ions accelerate forward so that they have the same kinetic energy, but reach
different velocities due to their varying masses. (lighter → faster)
Describe ion drift: [2] -answers - Some of the ions pass through a hole in the negatively
charged plate, forming a beam of particles. They travel along the 'flight tube' towards
the detector.
- As the ions are travelling at different speeds, they drift apart further.
Describe detection: [2] -answers - When the positive ions hit the negatively charged
detection plate, they gain an electron.
- This generates a current, the size of which is proportional to the number of each type
of ion.
Describe data analysis: [1] -answers The signal from the detector is passed to a
computer which generates a mass spectrum from the current.
What does each peak on the graph represent? [2] -answers - Each peak represents
different isotope.
- Height gives relative abundance of each isotope.
Give the formula for relative atomic mass: [1] -answers (sum of abundances not 100)
Describe where electrons are found. [3] -answers - Found in shells, orbiting nucleus.
- Within each shell there are sub-shells.
- Within each sub-shell we find orbitals.
Define orbital. [1] -answers An orbital is a region within an atom that can hold up to two
electrons with opposite spins.
How many orbitals are there in...
a) an s sub-shell
b) a p sub-shell
c) a d sub-shell [3] -answers a) one s orbital
b) three p orbitals
c) five d orbitals
Define highest energy electron. [1] -answers The outer most electron on an atom or ion.
, What is stated by the Aufbau principle? [1] -answers Orbitals of lower energy are always
filled first.
What are the exceptions to the Aufbau principle? [3] -answers Cr - 3d5 4s2
Cu - 3d10 4s1
Define ionisation energy. [2] -answers The amount of energy needed to remove a mole
of electrons from a mole of atoms, in the gaseous state.
Units kJmol-1
Why does ionisation energy increase each time? [1] -answers The second electron is
removed from an ion that already has a positive charge.
Give the equation for 3rd ionisation energy. [1] -answers
State 3 factors affecting ionisation energy: [3] -answers - Atomic Radius
- Nuclear Charge
- Shielding
Explain how atomic radius affects ionisation energy. [2] -answers - How far the outer
electrons are from the attractive power of the nucleus.
- The further an outer electron from the attractive power of the nucleus, the less energy
is required to ionise it.
Explain how nuclear charge affects ionisation energy. [2] -answers - How many protons
are attracting the outer electron.
- The greater the nuclear charge, the stronger the attraction to the outer electron, so
more energy is required to ionise it.
Explain how shielding affects ionisation energy. [2] -answers - How many electrons are
between the nucleus and the outer electron so shielding the attractive power of the
nucleus.
- The more inner electrons there are, the more the nucleus is shielded and the less
energy is required to ionise the outer electron.
Explain the trend in ionisation energy down a group [3] -answers Ionisation energy
decreases going down the group.
- Atomic radius increases
- More shielding
Explain the general trend in ionisation energy across Period 3. [3] -answers General
increase in IE across Period 3, this is because...
- Across the period there is a greater nuclear charge.
- Same amount of shielding
