A Level Chemistry (A2) chapter 5: Group 2 MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
24 exam-style questions on Group 2, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Similarities and trends in the properties of the Group 2 metals, magnesium to barium24 questions
Ten Group 2 questions with answers
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. Beryllium is above magnesium in Group 2, and the Be2+ ion is smaller than the Mg2+ ion. Using the Group 2 trend in thermal stability, what would you predict about beryllium carbonate?
A
it decomposes at a higher temperature than barium carbonate
B
it does not decompose, because Be2+ is too small to polarise the carbonate ion
C
it decomposes at about the same temperature as calcium carbonate, because both cations are 2+
D
it decomposes at a lower temperature than magnesium carbonate
Show answer
Answer: D. A smaller 2+ cation has a higher charge density, so it polarises the carbonate ion even more than Mg2+ does. The C−O bond is weakened more, so BeCO3 should be the least stable to heat.
2. A 2.00 g sample of a Group 2 carbonate, MCO3, is heated strongly to constant mass. The mass falls by 0.596 g. Which carbonate was it? (Ar: Mg 24.3, Ca 40.1, Sr 87.6, Ba 137.3)
A
SrCO3
B
MgCO3
C
CaCO3
D
BaCO3
Show answer
Answer: A. The mass lost is CO2: 0.596/44.0 = 0.01355 mol, which equals the moles of MCO3. Mr = 2.00/0.01355 = 148, which matches SrCO3 (87.6 + 60.0 = 147.6).
3. Soluble barium compounds are toxic, yet patients swallow a suspension of barium sulfate before an X-ray of the gut. Why is this safe?
A
barium sulfate is covalent and contains no Ba2+ ions
B
stomach acid turns barium sulfate into barium chloride, which is harmless
C
Ba2+ ions are only toxic when they are combined with nitrate ions
D
barium sulfate is so insoluble that very few Ba2+ ions go into solution
Show answer
Answer: D. BaSO4 has a very low solubility, the lowest of the Group 2 sulfates, so the concentration of free Ba2+ ions available to be absorbed is tiny. Barium chloride is soluble and toxic.
4. Down Group 2, the nitrates need higher temperatures to decompose. Which change down the group is mainly responsible?
A
the charge on the cation increases, so it attracts the nitrate ion more strongly
B
the cation radius increases, so the cation polarises the nitrate ion less
C
the larger cation polarises the nitrate ion more
D
the metals become less reactive down the group
Show answer
Answer: B. All the cations are 2+, but they get larger down the group, so their charge density falls. A larger cation distorts the nitrate ion's electron cloud less, so its N−O bonds are weakened less and more heat is needed.
5. Saturated solutions of Mg(OH)2, Ca(OH)2, Sr(OH)2 and Ba(OH)2 are made at 25 °C. Which solution has the highest pH?
A
Mg(OH)2
B
Ca(OH)2
C
Ba(OH)2
D
Sr(OH)2
Show answer
Answer: C. Group 2 hydroxides become more soluble down the group, so saturated Ba(OH)2 has the highest [OH−] and the highest pH. Magnesium hydroxide is only sparingly soluble, giving a pH of only about 10.
6. Which equation shows the thermal decomposition of calcium nitrate?
A
Ca(NO3)2 → Ca(NO2)2 + O2
B
Ca(NO3)2 → CaO + N2O5
C
2Ca(NO3)2 → 2CaO + 2N2 + 5O2
D
2Ca(NO3)2 → 2CaO + 4NO2 + O2
Show answer
Answer: D. Group 2 nitrates decompose on heating to the metal oxide, brown nitrogen dioxide and oxygen. Forming a nitrite and oxygen is how most Group 1 nitrates decompose.
7. Why does barium carbonate need a higher temperature to decompose than magnesium carbonate?
A
Ba2+ is larger, so it distorts the carbonate ion more and strengthens its bonds
B
Ba2+ has a higher charge than Mg2+, so it holds the carbonate ion more tightly
C
barium is more electronegative than magnesium, so barium carbonate is more covalent
D
Ba2+ is larger, with a lower charge density, so it distorts the carbonate ion less
Show answer
Answer: D. Both ions are 2+, but Ba2+ is much larger, so its charge density is lower and it polarises the carbonate ion less. The C−O bonds are weakened less, so more heating is needed to release CO2.
8. Which pair contains the least soluble Group 2 hydroxide and the least soluble Group 2 sulfate?
A
Ba(OH)2 and MgSO4
B
Mg(OH)2 and BaSO4
C
Mg(OH)2 and MgSO4
D
Ba(OH)2 and BaSO4
Show answer
Answer: B. Down Group 2 the hydroxides become more soluble but the sulfates become less soluble. So magnesium hydroxide is the least soluble hydroxide and barium sulfate the least soluble sulfate.
9. How does the enthalpy change of solution of the Group 2 sulfates change from MgSO4 to BaSO4, and what does this mean for their solubility?
A
it becomes less exothermic (more endothermic), so the solubility decreases
B
it becomes more exothermic, so the solubility decreases
C
it becomes less exothermic, so the solubility increases
D
it stays the same, because the solubility depends only on the lattice energy
Show answer
Answer: A. Down the group the hydration enthalpy of the cation falls much more than the lattice energy of the sulfate (the large sulfate ion dominates the lattice spacing), so ΔHsol becomes less exothermic and the sulfates become less soluble.
10. Equal masses of calcium carbonate and strontium carbonate are heated in turn in a tube connected to limewater, using the same Bunsen flame. Which result and reason are correct?
A
the limewater turns milky sooner with SrCO3, because the larger Sr2+ ion polarises the carbonate ion more
B
the limewater turns milky sooner with SrCO3, because it has the larger Mr
C
the limewater turns milky sooner with CaCO3, because Ca2+ has a higher charge density and polarises the carbonate ion more
D
the limewater turns milky at the same time, because both cations have a 2+ charge
Show answer
Answer: C. CaCO3 decomposes at a lower temperature than SrCO3: the smaller Ca2+ ion distorts the carbonate ion more, weakening a C−O bond, so CO2 is released sooner.
24, each with the answer and a short explanation, across 1 topics: Similarities and trends in the properties of the Group 2 metals, magnesium to barium. Every chapter test draws ten of them, so you can take it many times.
Is the A Level Chemistry (A2) chapter 5 test free?
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How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
