AS AND A-LEVEL CHEMISTRY MARK SCHEME
EXAM SCRIPT 2026 QUESTIONS WITH FULL
SOLUTIONS GRADED A+
◉ Describe how molecules are ionised using electrospray ionisation
(4 marks). Answer: 1. Sample dissolved (in a volatile solvent)
(allow named solvent eg water or methanol)
2. (injected through) a needle or nozzle or capillary and at high
voltage/4000 volts or high potential
(allow needle is positively charged)
3. Gains a proton / H+
4. X + H+ → XH+
◉ Outline how the TOF mass spectrometer works (4 marks).
Answer: 1. Positive ions are accelerated by an electric field
(allow (ions) accelerated to a negative plate)
2. To a constant kinetic energy
3. Ions create a current when hitting the detector
4. The size of the current is proportional to the abundance of ions
hitting the plate and gaining an electron
,◉ The student rinses the burette with deionised water before filling
with
sodium hydroxide solution.
State and explain the effect, if any, that this rinsing will have on the
value of
the titre (2 marks). Answer: 1. Titre value would increase / larger
value
2. Because the sodium hydroxide solution would be more dilute
◉ The student used a wash bottle containing deionised water when
approaching the end-point to rinse the inside of the conical flask.
Explain why this improved the accuracy of the titration (1 mark).
Answer: 1. Idea that it ensures all ethanedioic acid / acid / sodium
hydroxide / alkali / reactants are in the mixture / solution / reaction
OR
the idea that some of the ethanedioic acid / acid / sodium hydroxide
/ alkali / reactants would be on the sides of the flask
◉ Explain why pentan-2-ol has a higher boiling point than pent-1-
ene (3 marks). Answer: 1. Pentan-2-ol has stronger intermolecular
forces
2. Pent-1-ene has van der Waals' forces (only)
3. Pentan-2-ol (also) has hydrogen bonds
, ◉ Explain why a fluoride ion is larger than a sodium ion (2 marks).
Answer: 1. Fluoride ion has (two) fewer protons/lower nuclear
charge
2. Weaker attraction between nucleus and (outer) electrons
◉ Explain, in terms of structure and bonding, why the melting point
of sodium fluoride is high (2 marks). Answer: 1. (Electrostatic)
forces of attraction between oppositely charged ions/Na+ and F-
2. Lots of energy needed to overcome/break forces
◉ Explain how the lone pairs of electrons on the oxygen atom
influence the
bond angle in oxygen difluoride (2 marks). Answer: 1. Lone pairs
repel more than bond pairs
2. Bond angle will be lower than regular tetrahedral angle
◉ Explain how permanent dipole-dipole forces arise between
hydrogen
chloride molecules (2 marks). Answer: 1. Difference in
electronegativity leads to bond polarity
2. And there is an attraction between delta positive on one molecule
and delta negative on another
EXAM SCRIPT 2026 QUESTIONS WITH FULL
SOLUTIONS GRADED A+
◉ Describe how molecules are ionised using electrospray ionisation
(4 marks). Answer: 1. Sample dissolved (in a volatile solvent)
(allow named solvent eg water or methanol)
2. (injected through) a needle or nozzle or capillary and at high
voltage/4000 volts or high potential
(allow needle is positively charged)
3. Gains a proton / H+
4. X + H+ → XH+
◉ Outline how the TOF mass spectrometer works (4 marks).
Answer: 1. Positive ions are accelerated by an electric field
(allow (ions) accelerated to a negative plate)
2. To a constant kinetic energy
3. Ions create a current when hitting the detector
4. The size of the current is proportional to the abundance of ions
hitting the plate and gaining an electron
,◉ The student rinses the burette with deionised water before filling
with
sodium hydroxide solution.
State and explain the effect, if any, that this rinsing will have on the
value of
the titre (2 marks). Answer: 1. Titre value would increase / larger
value
2. Because the sodium hydroxide solution would be more dilute
◉ The student used a wash bottle containing deionised water when
approaching the end-point to rinse the inside of the conical flask.
Explain why this improved the accuracy of the titration (1 mark).
Answer: 1. Idea that it ensures all ethanedioic acid / acid / sodium
hydroxide / alkali / reactants are in the mixture / solution / reaction
OR
the idea that some of the ethanedioic acid / acid / sodium hydroxide
/ alkali / reactants would be on the sides of the flask
◉ Explain why pentan-2-ol has a higher boiling point than pent-1-
ene (3 marks). Answer: 1. Pentan-2-ol has stronger intermolecular
forces
2. Pent-1-ene has van der Waals' forces (only)
3. Pentan-2-ol (also) has hydrogen bonds
, ◉ Explain why a fluoride ion is larger than a sodium ion (2 marks).
Answer: 1. Fluoride ion has (two) fewer protons/lower nuclear
charge
2. Weaker attraction between nucleus and (outer) electrons
◉ Explain, in terms of structure and bonding, why the melting point
of sodium fluoride is high (2 marks). Answer: 1. (Electrostatic)
forces of attraction between oppositely charged ions/Na+ and F-
2. Lots of energy needed to overcome/break forces
◉ Explain how the lone pairs of electrons on the oxygen atom
influence the
bond angle in oxygen difluoride (2 marks). Answer: 1. Lone pairs
repel more than bond pairs
2. Bond angle will be lower than regular tetrahedral angle
◉ Explain how permanent dipole-dipole forces arise between
hydrogen
chloride molecules (2 marks). Answer: 1. Difference in
electronegativity leads to bond polarity
2. And there is an attraction between delta positive on one molecule
and delta negative on another
