GCSE CHEMISTRY (9–1): PAST PAPER 1:
HIGHER TIER. ALL ASSESSMENT &
MARK SCHEME COMPREHENSIVE STUDY
GUIDE 2026 FULL QUESTIONS AND
SOLUTIONS GRADED A+
◍ What is the volume of oxygen needed for the reaction of Si2H6?.
Answer: The volume of oxygen for 30 cm3 of Si2H6 is calculated as 3.5 ×
30 = 105 cm3.
◍ Filtering excess zinc oxide.
Answer: Excess zinc oxide can be filtered off to separate it from the solution
after a reaction.
◍ What does the reaction of silicon dioxide with carbon show about silicon's
position in the reactivity series?.
Answer: The reaction shows that silicon is less reactive than carbon since
carbon can reduce silicon dioxide to silicon.
◍ Why is excess zinc oxide used instead of excess hydrochloric acid?.
Answer: Excess zinc oxide is used to ensure complete reaction and to avoid
excess acid, which could lead to unwanted side reactions.
◍ Why is aluminium more expensive than carbon?.
Answer: Aluminium is more expensive than carbon because it requires more
energy-intensive processes for extraction and production.
◍ Sodium ion formation.
Answer: The formation of a sodium ion can be represented by the equation:
Na⁺ + e⁻ → Na.
, ◍ Energy change in reactions.
Answer: The overall energy change during a chemical reaction, which can
be either exothermic (energy released) or endothermic (energy absorbed).
◍ What is the significance of the gradient in a temperature vs. mass graph?.
Answer: It represents the change in highest temperature per change in mass.
◍ What happens to chloride ions at the positive electrode during electrolysis?.
Answer: Chloride ions (Cl-) are discharged or oxidized to form chlorine gas
(Cl2) at the positive electrode.
◍ What should be done to ensure a fair test?.
Answer: Use the same conditions for each trial, including temperature and
concentration.
◍ Why is rubidium more reactive than potassium?.
Answer: Rubidium is more reactive than potassium due to its larger atomic
size and lower ionization energy, making it easier to lose its outer electron.
◍ What is the purpose of indicative content in the mark scheme?.
Answer: It serves as a guide for examiners and is not intended to be
exhaustive; other valid points should also be credited.
◍ Products below reactants.
Answer: In an energy profile diagram, if the level of products is below the
level of reactants, it indicates that energy has been released during the
reaction.
◍ How does the strength of an acid relate to its pH?.
Answer: The stronger an acid, the greater its ionization in solution, resulting
in a lower pH.
◍ Why must electrolysis products be kept apart?.
Answer: The products must be kept apart to prevent them from reacting with
each other, which could lead to undesirable side reactions.
◍ What are noble gases?.
Answer: Noble gases are a group of chemical elements in Group 0 of the
HIGHER TIER. ALL ASSESSMENT &
MARK SCHEME COMPREHENSIVE STUDY
GUIDE 2026 FULL QUESTIONS AND
SOLUTIONS GRADED A+
◍ What is the volume of oxygen needed for the reaction of Si2H6?.
Answer: The volume of oxygen for 30 cm3 of Si2H6 is calculated as 3.5 ×
30 = 105 cm3.
◍ Filtering excess zinc oxide.
Answer: Excess zinc oxide can be filtered off to separate it from the solution
after a reaction.
◍ What does the reaction of silicon dioxide with carbon show about silicon's
position in the reactivity series?.
Answer: The reaction shows that silicon is less reactive than carbon since
carbon can reduce silicon dioxide to silicon.
◍ Why is excess zinc oxide used instead of excess hydrochloric acid?.
Answer: Excess zinc oxide is used to ensure complete reaction and to avoid
excess acid, which could lead to unwanted side reactions.
◍ Why is aluminium more expensive than carbon?.
Answer: Aluminium is more expensive than carbon because it requires more
energy-intensive processes for extraction and production.
◍ Sodium ion formation.
Answer: The formation of a sodium ion can be represented by the equation:
Na⁺ + e⁻ → Na.
, ◍ Energy change in reactions.
Answer: The overall energy change during a chemical reaction, which can
be either exothermic (energy released) or endothermic (energy absorbed).
◍ What is the significance of the gradient in a temperature vs. mass graph?.
Answer: It represents the change in highest temperature per change in mass.
◍ What happens to chloride ions at the positive electrode during electrolysis?.
Answer: Chloride ions (Cl-) are discharged or oxidized to form chlorine gas
(Cl2) at the positive electrode.
◍ What should be done to ensure a fair test?.
Answer: Use the same conditions for each trial, including temperature and
concentration.
◍ Why is rubidium more reactive than potassium?.
Answer: Rubidium is more reactive than potassium due to its larger atomic
size and lower ionization energy, making it easier to lose its outer electron.
◍ What is the purpose of indicative content in the mark scheme?.
Answer: It serves as a guide for examiners and is not intended to be
exhaustive; other valid points should also be credited.
◍ Products below reactants.
Answer: In an energy profile diagram, if the level of products is below the
level of reactants, it indicates that energy has been released during the
reaction.
◍ How does the strength of an acid relate to its pH?.
Answer: The stronger an acid, the greater its ionization in solution, resulting
in a lower pH.
◍ Why must electrolysis products be kept apart?.
Answer: The products must be kept apart to prevent them from reacting with
each other, which could lead to undesirable side reactions.
◍ What are noble gases?.
Answer: Noble gases are a group of chemical elements in Group 0 of the
