HGSCS CSSUYSGDVS DSUYSD78D9WIHBD SCKCUGGD DSSUDY89EIHWB SS,CKJU9UDSIDSHVD S
Oxford Cambridge and RSA
YTGDV DDJUGYV CXKCIUGDVSD SKUGSIDDNNXIOI;SKDLSB CXKCJUCIOJKJBSSKICUISJKBCXCUCIOKLSKJSHS
EFEUDHEY6TYUHJBJBW WIWWYVH WIE789EIHBW SDK987EYEV DSDMSDU89E02OEK EW,DKIDGD
A-Level OCR 2025 Chemistry B (Salters) Paper 3
Friday 20 June 2025 – Morning
A Level Chemistry B (Salters)
H433/03 Practical skills in chemistry
Time allowed: 1 hour 30 minutes
1
Turn over
, 2
1 This question is about the properties of some Group 2 alkaline earth metals and their compounds.
(a)
(i) The term ‘alkaline’ refers to oxides and hydroxides of the Group 2 elements.
Explain why calcium oxide is described as alkaline.
Include an appropriate equation.
Explanation: .....................................................................................................................................
..........................................................................................................................................................
Equation:
[2]
(ii) Explain why the Group 2 elements are known as s block elements.
..........................................................................................................................................................
...................................................................................................................................................................... [1]
(b) Strontium sulfate is used in fireworks. Strontium gives a red colour when ignited.
A frequency of red light from the strontium spectrum is 4.62 × 1014 Hz.
Calculate the energy per mole of photons of this frequency in kJ mol–1.
Give your answer to an appropriate number of significant figures.
Energy = ........................................... kJ mol–1 [3]
© OCR 2025
, 3
(c) Barium sulfate is very insoluble in water.
(i) Solutions containing sulfate ions give a white precipitate with barium chloride solution.
Write an ionic equation for the formation of this white precipitate.
Include state symbols.
[1]
(ii) A solution has [SO4 2–] = 0.10 mol dm–3.
Calculate the smallest [Ba2+] in the solution which will just give a white precipitate.
For barium sulfate, Ksp = 1.0 × 10–10 mol2 dm–6.
[Ba2+] = .......................................... mol dm–3 [2]
(d) Calcium and potassium are in the same period of the periodic table.
Explain why calcium has the higher melting point.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
...................................................................................................................................................................... [2]
© OCR 2025 Turn over
Oxford Cambridge and RSA
YTGDV DDJUGYV CXKCIUGDVSD SKUGSIDDNNXIOI;SKDLSB CXKCJUCIOJKJBSSKICUISJKBCXCUCIOKLSKJSHS
EFEUDHEY6TYUHJBJBW WIWWYVH WIE789EIHBW SDK987EYEV DSDMSDU89E02OEK EW,DKIDGD
A-Level OCR 2025 Chemistry B (Salters) Paper 3
Friday 20 June 2025 – Morning
A Level Chemistry B (Salters)
H433/03 Practical skills in chemistry
Time allowed: 1 hour 30 minutes
1
Turn over
, 2
1 This question is about the properties of some Group 2 alkaline earth metals and their compounds.
(a)
(i) The term ‘alkaline’ refers to oxides and hydroxides of the Group 2 elements.
Explain why calcium oxide is described as alkaline.
Include an appropriate equation.
Explanation: .....................................................................................................................................
..........................................................................................................................................................
Equation:
[2]
(ii) Explain why the Group 2 elements are known as s block elements.
..........................................................................................................................................................
...................................................................................................................................................................... [1]
(b) Strontium sulfate is used in fireworks. Strontium gives a red colour when ignited.
A frequency of red light from the strontium spectrum is 4.62 × 1014 Hz.
Calculate the energy per mole of photons of this frequency in kJ mol–1.
Give your answer to an appropriate number of significant figures.
Energy = ........................................... kJ mol–1 [3]
© OCR 2025
, 3
(c) Barium sulfate is very insoluble in water.
(i) Solutions containing sulfate ions give a white precipitate with barium chloride solution.
Write an ionic equation for the formation of this white precipitate.
Include state symbols.
[1]
(ii) A solution has [SO4 2–] = 0.10 mol dm–3.
Calculate the smallest [Ba2+] in the solution which will just give a white precipitate.
For barium sulfate, Ksp = 1.0 × 10–10 mol2 dm–6.
[Ba2+] = .......................................... mol dm–3 [2]
(d) Calcium and potassium are in the same period of the periodic table.
Explain why calcium has the higher melting point.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
...................................................................................................................................................................... [2]
© OCR 2025 Turn over
