AQA A LEVEL CHEMISTRY PAPER 1
QUESTIONS WITH COMPLETE ANSWERS
2025.
TOF steps - ANSWER: 1) ionisation
2) acceleration
3) ion drift
4) detection
5) analysis
Electron impact - ANSWER: Sample vaporised and electron gun fires high energy
electrons at it which knock off 1 electron from each particle, making them 1+ ions
NB- can knock off more than one e or break molecular ion
electrospray ionization - ANSWER: Sample dissolved in volatile solvent then injected
through needle to give fine mist which is attached to positive end of high voltage power
supply, particles gain proton
NB- Mr of substance is actually one less than shown due to extra H+
Acceleration (TOF) - ANSWER: positive ions accelerated using electric field so they all
have the same kinetic energy
Ion drift (TOF) - ANSWER: particles with small mass have larger velocity do ions start to
separate with lightest ions reaching detector first
Detection (TOF) - ANSWER: positive ions hit negatively charged plate and gain an
electron which forms a current, the larger the current the higher the abundance
, Analysis (TOF) - ANSWER: -computer uses data to produce mass spectrum which
shows mass m / charge z ratio
-mr or ar is furthest right peak (small peaks larger than mr are due to isotopes)
-may be large peaks at lower mr due to fragmentation
Electron spin - ANSWER: Property of electron (CW or ACW)
Represented by up and down arrows
Orbitals - ANSWER: Defined regions of space around nucleus where electrons most
likely to be found, each orbital holds 2 electrons
Hund's Rule - ANSWER: Electrons prefer to occupy orbitals on their own and only pair
up when no empty or bait ask of same energy are available
Electron configuration - ANSWER: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10
exceptions to electron configuration - ANSWER: chromium and copper, only take one
electron in 4s orbital
Why does ionization energy decrease down a group? - ANSWER: Atoms get bigger so
electrons further away from nucleus, greater shielding
Why does ionization energy increase across a period? - ANSWER: Atoms get smaller,
nuclear charge increases, similar shielding
Dip in ionisation energy groups 2-3 - ANSWER: Electrons take up higher orbital (s to p)
which makes ionisation energy lower as higher orbitals have higher energy
Dip in ionisation energy groups 5-6 - ANSWER: Electron- electron repulsion in orbital
makes electron easier to lose
Relative atomic mass - ANSWER: The average mass of an atom of an element/ 1/12th
of the mass of an atom of carbon-12
Empirical formula - ANSWER: The simplest whole number ratio of atoms of each
element present in a compound
Percentage yield - ANSWER: actual yield/theoretical yield x 100
Atom economy - ANSWER: (Molecular mass of desired products/ Molecular mass of all
products) x 100
QUESTIONS WITH COMPLETE ANSWERS
2025.
TOF steps - ANSWER: 1) ionisation
2) acceleration
3) ion drift
4) detection
5) analysis
Electron impact - ANSWER: Sample vaporised and electron gun fires high energy
electrons at it which knock off 1 electron from each particle, making them 1+ ions
NB- can knock off more than one e or break molecular ion
electrospray ionization - ANSWER: Sample dissolved in volatile solvent then injected
through needle to give fine mist which is attached to positive end of high voltage power
supply, particles gain proton
NB- Mr of substance is actually one less than shown due to extra H+
Acceleration (TOF) - ANSWER: positive ions accelerated using electric field so they all
have the same kinetic energy
Ion drift (TOF) - ANSWER: particles with small mass have larger velocity do ions start to
separate with lightest ions reaching detector first
Detection (TOF) - ANSWER: positive ions hit negatively charged plate and gain an
electron which forms a current, the larger the current the higher the abundance
, Analysis (TOF) - ANSWER: -computer uses data to produce mass spectrum which
shows mass m / charge z ratio
-mr or ar is furthest right peak (small peaks larger than mr are due to isotopes)
-may be large peaks at lower mr due to fragmentation
Electron spin - ANSWER: Property of electron (CW or ACW)
Represented by up and down arrows
Orbitals - ANSWER: Defined regions of space around nucleus where electrons most
likely to be found, each orbital holds 2 electrons
Hund's Rule - ANSWER: Electrons prefer to occupy orbitals on their own and only pair
up when no empty or bait ask of same energy are available
Electron configuration - ANSWER: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10
exceptions to electron configuration - ANSWER: chromium and copper, only take one
electron in 4s orbital
Why does ionization energy decrease down a group? - ANSWER: Atoms get bigger so
electrons further away from nucleus, greater shielding
Why does ionization energy increase across a period? - ANSWER: Atoms get smaller,
nuclear charge increases, similar shielding
Dip in ionisation energy groups 2-3 - ANSWER: Electrons take up higher orbital (s to p)
which makes ionisation energy lower as higher orbitals have higher energy
Dip in ionisation energy groups 5-6 - ANSWER: Electron- electron repulsion in orbital
makes electron easier to lose
Relative atomic mass - ANSWER: The average mass of an atom of an element/ 1/12th
of the mass of an atom of carbon-12
Empirical formula - ANSWER: The simplest whole number ratio of atoms of each
element present in a compound
Percentage yield - ANSWER: actual yield/theoretical yield x 100
Atom economy - ANSWER: (Molecular mass of desired products/ Molecular mass of all
products) x 100
