AS AND A-LEVEL CHEMISTRY MARK SCHEME
ACTUAL TEST 2026 QUESTIONS WITH
VERIFIED ANSWERS GRADED A+
◉ Average bond enthalpy. Answer: Bonds broken in reactants -
bonds made in products
◉ A student calculates the pH so HIO3 (Ka = 1.78 x 10^-1). Student
assumes initial HIO3 concentration is equal to equilibrium [HIO3].
She m finds measured pH is different from calculate value. Explain
why? (1) Answer: 1. Dissociation fo HIO3 is not negligible AND HIO3
is a 'stronger weak acid' due to large Ka value
◉ Previously, excess of magnesium added to 100cm3 of 0.4 moldm^-
3 AgNO3. Now excess Mg added to 50cm3 0.4moldm^-3 AgNO3.
Predict how modification would affect maximum temperature
reached Answer: 1. Maximum temperature is the same
2. Although number of moles of solution halves, volume of solution
also halves therefore same change in temperature (half the moles
halves the energy but spread over half the volume therefore same
change in t)
◉ For strong acid weak base pH curves, what pH is equivalence
point (half way up vertical section)? Answer: Less than 7
, ◉ Calculate the total number of ions in 7.41g of Calcium hydroxide
Answer: (Number of moles x avagadro's constant) x 3 (as Ca(OH)2
dissociates to form 3 ions
◉ Reason for getting a smaller tire than expected? Answer: 1. Rinsed
the pipette with water before filling with base (smaller volume
therefore smaller number of moles of OH-)
◉ In electron configuration of Sr2+ atom, what fills first, 4d2 or 5s2?
Answer: 5s2
◉ Weighted mean mass Answer: Average mass of an element taking
into account the real tic percentage abundances of its isotopes
◉ Relative isotopic mass Answer: The mass of an atom of an isotope
compared with one-twelfth of the mass of an atom of carbon-12.
◉ Relative atomic mass Answer: The weighted mean mass of an
atom of an element compared with one-twelfth of the mass of an
atom of carbon-12.
◉ London forces BETWEEN Answer: Molecules
ACTUAL TEST 2026 QUESTIONS WITH
VERIFIED ANSWERS GRADED A+
◉ Average bond enthalpy. Answer: Bonds broken in reactants -
bonds made in products
◉ A student calculates the pH so HIO3 (Ka = 1.78 x 10^-1). Student
assumes initial HIO3 concentration is equal to equilibrium [HIO3].
She m finds measured pH is different from calculate value. Explain
why? (1) Answer: 1. Dissociation fo HIO3 is not negligible AND HIO3
is a 'stronger weak acid' due to large Ka value
◉ Previously, excess of magnesium added to 100cm3 of 0.4 moldm^-
3 AgNO3. Now excess Mg added to 50cm3 0.4moldm^-3 AgNO3.
Predict how modification would affect maximum temperature
reached Answer: 1. Maximum temperature is the same
2. Although number of moles of solution halves, volume of solution
also halves therefore same change in temperature (half the moles
halves the energy but spread over half the volume therefore same
change in t)
◉ For strong acid weak base pH curves, what pH is equivalence
point (half way up vertical section)? Answer: Less than 7
, ◉ Calculate the total number of ions in 7.41g of Calcium hydroxide
Answer: (Number of moles x avagadro's constant) x 3 (as Ca(OH)2
dissociates to form 3 ions
◉ Reason for getting a smaller tire than expected? Answer: 1. Rinsed
the pipette with water before filling with base (smaller volume
therefore smaller number of moles of OH-)
◉ In electron configuration of Sr2+ atom, what fills first, 4d2 or 5s2?
Answer: 5s2
◉ Weighted mean mass Answer: Average mass of an element taking
into account the real tic percentage abundances of its isotopes
◉ Relative isotopic mass Answer: The mass of an atom of an isotope
compared with one-twelfth of the mass of an atom of carbon-12.
◉ Relative atomic mass Answer: The weighted mean mass of an
atom of an element compared with one-twelfth of the mass of an
atom of carbon-12.
◉ London forces BETWEEN Answer: Molecules
