CIE A Level Chemistry

Topic Questions

A LevelChemistryCIETopic Questions6. Inorganic Chemistry (A Level Only)6.1 Group 2 (A Level Only)

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First teaching 2020

Last exams 2024

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6.1 Group 2 (A Level Only)

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1a3 marks

This question is about Group 2 carbonates. 

Magnesium carbonate is used as an antacid and used to treat heartburn. 

i)
Write the chemical formula of magnesium carbonate. 
[1]
ii)
Write a balanced symbol equation for the reaction of magnesium carbonate with dilute nitric acid. 
[2]

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1b2 marks
i)
From the list below, identify the compound that will decompose at the lowest temperature. 

  • calcium carbonate
  • strontium carbonate
  • barium carbonate

[1]

ii)
Write a balanced symbol equation for the decomposition of your chosen carbonate. 
[1]

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1c2 marks

Group 2 nitrates become more thermally stable going down the group. 

Explain why.

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2a3 marks

This question is about Group 2 compounds. 

Strontium will react with water. 

i)
Write a balanced symbol equation for the reaction. 
[2]
ii)
Describe a test to identify the gas produced. 
[1]

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2b3 marks

Calcium hydroxide reacts with sulfuric acid to produce calcium sulfate and water.

i)
Write the balanced symbol equation for this reaction. 
[2]
ii)
Describe the trend in the solubility of the Group 2 sulfates. 
[1]

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2c2 marks

The trend in solubility of the Group 2 sulfates is due to the lattice energy, ΔHθlatt, and enthalpy change of hydration, ΔHθhyd , of the Group 2 sulfates changing. 

Describe the trend in ΔHθlatt and ΔHθhyd of Group 2 sulfates going down Group 2. 

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3a2 marks

The elements in Group 2 from Mg to Ba can be used to show the trends in properties down a group in the Periodic Table. 

The Group 2 elements react with water. 

i)
State the trend in reactivity with water of the elements down Group 2 from Mg to Ba. 

[1]

ii)
Predict a possible pH for the solutions formed when Group 2 elements are added to water.

[1]

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3b1 mark

Give the formula of the hydroxide of the element in Group 2 from Mg to Ba that is most soluble in water.

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3c4 marks

A trend in the thermal decomposition of Group 2 nitrates can also be observed.

i)
Give the oxidation number of nitrogen in Ca(NO3)2.
[1]
ii)
Write an equation for the thermal decomposition of Ca(NO3)2.
[2]
iii)
State the trend in thermal stability of Group 2 nitrates.
  [1] 

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1a
Sme Calculator3 marks

This question is about magnesium. 

Magnesium forms a nitrate, Mg(NO3)2 which decomposes on heating as shown below:

2Mg(NO3)2 (s) →   2MgO (s) + 4NO2 (g) + O2 (g)

Using oxidation numbers, explain why the reaction involves both oxidation and reduction. 

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1b8 marks
The values for the first, second and third ionisation energies of magnesium are shown in Table 1.1.







Table 1.1

  Ionisation energy / kJ mol-1
First ionisation energy  738
Second ionisation energy 1451
Third ionisation energy  7732

i)
Write an equation for the second ionisation energy of magnesium.
 
[2]
 
ii)
Explain the trend in the first three ionisation energies of magnesium.
 
[3]
 
iii)

Explain why magnesium has a greater second ionisation energy than barium.

 
[3]
 
   
                                                               

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1c4 marks

Metal peroxides contain the –O–O– ion.

The peroxides of the Group 2 elements, MO2, decompose in a similar way to Group 2 metal carbonates. 

i)
Write an equation for the thermal decomposition of strontium peroxide, SrO2.
 
[1]
 
ii)
Suggest how the temperature at which thermal decomposition of MO2 occurs varies down Group 2. Explain your answer.
 
[3]

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2a2 marks

Table 2.1 below shows the solubility data for the Group 2 metal hydroxides.

Table 2.1

Group 2 metal hydroxide

Solubility / g dm-3 at 20 °C

Magnesium hydroxide

0.140

Calcium hydroxide

1.730

Strontium hydroxide

17.70

Barium hydroxide

38.90

State and explain the factors responsible for the trend in the solubility of the Group 2 hydroxides.

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2b2 marks

Milk of magnesia, Mg(OH)2 is used to neutralise stomach acid.

Explain why Mg(OH)2 cannot be used to test for carbon dioxide but Ba(OH)2 can. 

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2c
Sme Calculator3 marks
i)
Write an expression for the solubility product of Sr(OH)2  
 
Ksp =
 
[1]
 
ii)
Use the data from Table 3.1 in part (a) to calculate the value of Ksp at 293 K. Include units in your answer and show your working.
 
 
 
Ksp = ................................................ units = ..............................
[2]

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2d
Sme Calculator5 marks

Use the data from Table 3.1 in part (a) to calculate the pH of a saturated solution of Mg(OH)2 at 293 K. Show your working.

Kw at 293 K = 0.681 x 10-14 mol2 dm-6



pH = ......................

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3a
Sme Calculator6 marks

Calcium carbonate can be thermally decomposed to make calcium oxide. 

CaCO3 (s) → CaO (s) + CO2 (g)   ΔH = + 178 kJ mol-1

Table 3.1 below shows the standard entropies of each substance. 

Table 3.1

Substance CaCO3 (s) CaO (s) CO2 (g)
S / J K–1 mol–1 89 40 214

i )
Use the information in Table 3.1 to show that calcium carbonate is stable at room temperature (25 oC).
 
[4]
 
ii)
Calculate the minimum temperature needed to decompose calcium carbonate.
 
[2]

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3b3 marks

Describe and explain the trend that is observed in the thermal decomposition of the Group 2 carbonates. 

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3c3 marks
i)
Write an equation to show the equilibrium for the solubility product for CaCO3. Include state symbols.
[1]

ii)
With reference to your equation in part (c)(i), suggest what is observed when a few cm3 of concentrated K2CO3 (aq) are added to a saturated solution of CaCO3. Explain your answer.
[2]

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3d
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CaCO3 has a solubility product, Ksp in water at 298 K of 5 x 10-9 mol2 dm–6 

Calculate the solubility of CaCO3 in water at 298 K, in g dm–3


solubility of CaCO3 = ............................. g dm–3

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1a2 marks

This question is about Group 2 nitrates. 

Strontium nitrate is is a Group 2 nitrate used to produce a colour in fireworks. 

i)
Give the formula of strontium nitrate. 

[1]
ii)
Give the colour that strontium nitrate will give in fireworks. 

[1]

How did you do?

1b1 mark
i)
Write an equation for the reaction that occurs when strontium nitrate is heated.
You should include state symbols. 
[2]
ii)
Give one observation of this reaction. 

[1]

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1c3 marks

The nitrate ion, NO3 , contains a dative covalent bond.

Complete the following ‘dot-and-cross’ diagram of the bonding in the nitrate ion.

Use the following code for your electrons:

•  electrons from oxygen
x electrons from nitrogen
□ added electron(s) responsible for the overall negative charge

sRt1hGoO_6-1-1c-m-nitrate-ion-dot-and-cross-diagram-1

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1d1 mark

Describe and explain the trend in thermal stabilities of the nitrates of the Group 2 elements. 

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2a2 marks

Magnesium is a Group 2 metal. 

Write an equation, including state symbols for the reaction between:

i)
magnesium and steam

[1]
ii)
magnesium and sulfuric acid

[1]

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2b4 marks

Magnesium sulfate is soluble in water. 

Describe and explain how the solubilities of the sulfates of the Group II elements vary down the group.

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2c
Sme Calculator2 marks

The following table lists some enthalpy changes for magnesium and strontium compounds

Enthalpy change 

Value for magnesium 

/ kJ mol-1

Value for strontium

/ kJ mol-1
 lattice enthalpy of M(OH)2 -2993 -2467
 enthalpy change of hydration of M2+(g) -1890 -1414
 enthalpy change of hydration of OH–(g) -550 -550

Use the above data to calculate values of ΔHθsol for Mg(OH)2 and for Sr(OH)2.

Mg(OH)2    .....................................  kJ mol-1 

Sr(OH)2.     ....................................  kJ mol-1 

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2d2 marks

Use your results from part (c) to suggest whether Sr(OH)2 is more or less soluble in water than in Mg(OH)2, assuming all other factors are the same.

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3a3 marks

This question is about Group 2 carbonates. 

Group 2 carbonates can react with acids.

i)
Compare the reaction of calcium carbonate with hydrochloric acid and sulfuric acid.
[2]
ii)
Write an equation for the reaction between calcium carbonate and sulfuric acid, including state symbols. 

[1]

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3b3 marks

Describe and explain the trend observed in the thermal stability of the carbonates of the Group II elements.

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3c2 marks

The ionic radii of three ions are shown in Table 4.1.


Suggest how the thermal stabilities of zinc carbonate and lead carbonate might compare to that of calcium carbonate. 



Table 4.1 

Ion Ionic radii (nm)
Ca2+ 0.099
Zn2+ 0.074
Pb2+ 0.120

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3d4 marks

Zinc is found in d block of the Periodic table but is not a transition element. 

i)
Explain why zinc is not classed as a transition element. 

[1]

ii)
Describe three characteristic chemical properties of transition elements that are not shown by Group 2 elements. 

[3]

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4a2 marks

This question is about Group 2 hydroxides.

Samples of magnesium, calcium, strontium and barium are reacted with water to form their hydroxides. The resulting solutions are then filtered to collect the precipitates.

Explain the trend in the expected mass for the precipitates.

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4b2 marks

Table 4.1 shows the solubility data for the Group 2 metal hydroxides.

Table 4.1

Group 2 metal hydroxide

Solubility / g dm-3 at 20 °C

Magnesium hydroxide

0.140

Calcium hydroxide

1.730

Strontium hydroxide

17.70

Barium hydroxide

38.90

A student determined that a 50 cm3 solution of an unknown Group 2 metal hydroxide contained 802 mg of the metal hydroxide.

Identify the metal hydroxide in the unknown sample.

How did you do?

4c2 marks

Write an equation for the reaction between magnesium hydroxide and sulfuric acid. 

You should include state symbols. 

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4d5 marks

The solubility of Group 2 hydroxides increases going down the group because the enthalpy of solution, ΔHθsol, gets more exothermic. 

i)
Define the term enthalpy of solution, ΔHθsol.
 

[2]

ii)
Explain why going down Group 2 the enthalpy of solution, ΔHθsol  gets more exothermic. 

[3]

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