Group 2, the Alkaline Earth Metals (AQA AS Chemistry)

Exam Questions

3 hours44 questions
1a3 marks
i)
State how many electrons a Group 2 element has in its outermost principal quantum shell.

ii)
State how a Group 2 element forms an ionic bond with nonmetals.

iii)
State whether Group 2 elements act as oxidising or reducing agents.
1b5 marks
i)
Write an equation to show the first ionisation of a Group 2 metal, M.

ii)
Describe the trend in first ionisation energy as you move down Group 2.

iii)
Explain the trend in first ionisation energy as you move down Group 2.
1c2 marks
i)
Describe the trend in atomic radius as you move down Group 2.

ii)
Describe the relationship between atomic radius and melting point as you move down Group 2.
1d1 mark

The density of the Group 2 elements is shown in Figure 1.

Figure 1

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Describe the trend in density as you move down Group 2.

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2a4 marks
i)
Write a balanced symbol equation for an aqueous Group 2 metal hydroxide, M(OH)2, dissociating into its component ions in solution.

ii)
The solubilities of the Group 2 hydroxides, from magnesium to barium, are shown in Table 1.

Table 1

Group 2 hydroxide

Solubility at 298 K (mol / 100 g of water)

Mg(OH)2

2.0 x 10-5

Ca(OH)2

1.5 x 10-3

Sr(OH)2

3.4 x 10-3

Ba(OH)2

1.5 x 10-2

 

Describe the trend in solubility of the Group 2 hydroxides as you move down the group

iii)
Use your answers to parts (i) and (ii) to explain the trend in pH of the Group 2 metal hydroxides as you move down the group.
2b3 marks
i)
Write the balanced symbol equation, including state symbols, for the reaction of a Group 2 metal, M, with sulfuric acid to form a salt and hydrogen.

ii)
Describe the trend in the solubility of the Group 2 metal sulfates as you move down the group.
2c2 marks

Magnesium hydroxide forms a white precipitate in water, while magnesium sulfate forms a colourless solution in water.

i)
State the expected appearance of barium hydroxide in water.

ii)
State the expected appearance of barium sulfate in water.
2d3 marks

The insoluble hydroxide and sulfate precipitates formed by magnesium and barium have medicinal uses. The magnesium precipitate is used as an indigestion remedy.

i)
Name the white barium precipitate that has a medicinal use.

ii)
State what the white barium precipitate is used for.

iii)
Suggest why the white barium precipitate is safe to use when barium ions are toxic.

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3a3 marks

Write two balanced symbol equations, including state symbols, for the reaction of strontium with oxygen.

3b3 marks

Write the balanced symbol equation, including state symbols, for the reaction of strontium oxide, SrO, with hydrochloric acid to form a salt and one other product.

3c2 marks

Write the balanced symbol equation, including state symbols, for the reaction of strontium with sulfuric acid to form a salt and one other product.

3d3 marks

Write the balanced symbol equation, including state symbols, for the reaction of strontium carbonate with nitric acid to form a salt and two other products.

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4a1 mark

Describe the trend in the reactions of the Group 2 metals with water.

4b3 marks

Write a balanced symbol equation, including state symbols, for the feasible reaction of a named Group 2 metal with cold water to form the Group 2 metal hydroxide and one other product.

4c1 mark

Name the type of reaction taking place when Group 2 metal hydroxides react with hydrochloric acid according to the following equation:

M(OH)2 + 2HCl → MCl2 + 2H2O

4d4 marks
i)
Write a balanced symbol equation, including state symbols, for the reaction between barium hydroxide and sulfuric acid.

ii)
What observations would you expect to see during the reaction between barium hydroxide and sulfuric acid?

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5a3 marks

Complete Table 1 showing the common names, chemical names and chemical formulae of various “Lime” chemicals.

Table 1

Common name

Chemical name

Chemical formula with state symbol

 

Calcium carbonate

CaCO3 (s)

Quicklime

Calcium oxide

 

Slaked lime

 

Ca(OH)2 (aq)

5b1 mark

What does the agricultural industry use all three “Lime” chemicals for?

5c3 marks
i)
State two reasons why calcium carbonate is used in agricultural lime.

ii)
State one disadvantage of using calcium carbonate in agricultural lime.
5d1 mark

Wet scrubbing is used in fossil fuel power stations. This reacts calcium carbonate and water with sulfur dioxide from the flue gases. Calcium sulfite, CaSO3, water and carbon dioxide are produced during this reaction.

Write the balanced symbol equation for this reaction.

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1a2 marks

Different groups of the Periodic Table demonstrate different trends as you descend that group. Magnesium to barium demonstrate the trends in properties shown down Group 2 of the Periodic Table.

Give the formulas of the Group 2 hydroxide and the Group 2 sulfate, from magnesium to barium, which are the least soluble in water.

1b2 marks

The solubility of barium sulfate means that it is extremely useful in medicine. 

Give a medical use of barium sulfate and state why it is safe to use, despite solutions containing Ba2+ ions being toxic. 

1c3 marks

The elements of Group 2 will react with water.

State the trend shown in the reactivity of the elements of Group 2 (Mg - Ba) when they react with water and give the equations for the reactions of magnesium with cold water and with steam.

Include state symbols in your equations.

 

1d3 marks

Identify the element of Group 2, from  calcium to barium, which has the lowest melting point.

State and explain the general trend in melting point as you descend Group 2 of the Periodic Table.

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2a1 mark

Give the full electron configuration for a magnesium ion, Mg2+.

2b4 marks

Identify the element in Group 2 from magnesium to barium which has the lowest first ionisation energy.

Explain your answer. 

2c4 marks

A group of students completed two experiments. In experiment 1, they added magnesium metal to nitric acid and in experiment 2, they added calcium metal to sulfuric acid. The students then compared the two reactions and found that a white solid had been produced in experiment 2.

The concentration of each acid was kept the same and the mass of each Group 2 metal used was also kept the same.

Predict and explain which reaction would finish first, and name the white solid formed.

2d2 marks

Write equations for the reactions taking place in Experiment 1 and Experiment 2. 

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3a2 marks

Magnesium, calcium and barium are some of the Group 2 elements of the Periodic Table. 

State and explain the trend in atomic radius of the Group 2 elements from magnesium to barium.

3b2 marks

Magnesium is frequently used in fireworks. It burns rapidly in oxygen, and it adds sparks which generally improves the appearance and brilliance of the firework.

Write an equation to represent the reaction which takes place when a strip of magnesium is burned in oxygen and state an observation which would be made.

3c5 marks

Group 2 compounds, such as the hydroxides of magnesium and calcium, have a number of other uses. 

i)
Write equations to show the formation of magnesium hydroxide and calcium hydroxide from their metals. 

ii)
Give an approximate pH value and a use of each of the hydroxides.
3d3 marks

Group 2 elements will react with water.

A student added 20cm3 of water to two boiling tubes. To one of the boiling tubes they added a small piece of calcium and to the other they added a small piece of barium.

State two observations that the student would make and how the observations would differ between the two boiling tubes.

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4a2 marks

Barium is a Group 2 element whose compounds have a number of uses. Barium chloride solution is used to test for sulfate ions, but it must be acidified before it can be used.

i)
State why sulfuric acid could not be used to acidify the barium chloride solution. 

ii)
Write the simplest ionic equation to demonstrate how barium chloride solution is used to test for sulfate ions. 
4b2 marks

Name the type of reaction taking place in part (a) and give a use of the product formed from this reaction. 

4c2 marks

The solubility of compounds of Group 2 elements vary down the group.

State the trends in solubility of the Group 2 sulfates and the Group 2 hydroxides as you descend the group. 

4d3 marks

Compare the reactivity of barium with the reactivity of magnesium. Explain your answer.

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5a1 mark

This question is about Group 1 and Group 2 metals of the Periodic Table.

Give the electron configuration of the s block metal which has the highest first ionisation energy.

5b3 marks

Explain why the first ionisation energy of the element in part (a) is higher than the first ionisation energy of calcium.

5c5 marks

A student has completed a number of simple test tube reactions to determine the identity of some unlabelled solutions.

The student has only two solutions left which they need to identify. One of the solutions is sodium nitrate and the other is sodium sulfate.

i)
Describe one simple test tube reaction that the student could do, to distinguish between the two solutions and write the simplest ionic equation for any reaction which occurs.

ii)
Explain why the observation would be different for each solution.
5d3 marks

Magnesium is another Group 2 element which undergoes a number of chemical reactions.

A teacher is completing a demonstration for class, reacting magnesium ribbon with steam.

State two observations that the students would make during the demonstration and provide an equation, with state symbols, for the reaction which is taking place.

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1a1 mark

Magnesium reacts very slowly with water to form magnesium hydroxide and hydrogen. 

A student suggests that when magnesium reacts with steam, it should just produce magnesium hydroxide and hydrogen but at a quicker rate.

Write a balanced symbol equation to demonstrate the thermal instability of one of the student’s suggested products. You are not required to write the correct equation for the reaction of magnesium with steam.

1b1 mark

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.

State the trend in the expected mass for the precipitates.

1c3 marks

Explain how the following trends of Group 2 metal hydroxides, from Mg - Ba, are connected:

  • Solubility in water
  • Strength as a base

1d2 marks

Table 1 shows the solubility data for the Group 2 metal hydroxides.

Table 1

Group 2 metal hydroxide

Solubility / g dm-3 at 20 bold degreeC

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.

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2a1 mark

A student is asked to determine the identity of an impure Group (II) metal sample.

The impure sample was known to contain only sulfate-based chemicals. It appeared to be a white solid which formed a white precipitate in a pale blue solution when dissolved in
25.0 cm3 of water.

Suggest the identity of the impurity in the unknown sample.

2b1 mark

Table 1 shows the solubility of the Group 2 metal sulfates at 20 degreeC.

Table 1

Group 2 metal sulfate

Solubility / g per 100 cm3 

Magnesium sulfate

7.38 x 101 

Calcium sulfate

2.09 x 10-1

Strontium sulfate

1.13 x 10-2

Barium sulfate

2.20 x 10-4

Use the information in Table 1 to explain which Group (II) metal sulfate cannot be the unknown metal sulfate in the sample from part (a).

2c3 marks

The student analysed a 2.50 g sample of the impure Group 2 metal sulfate.

They found the sample to be 94.4 % pure and that 0.12 % of the Group 2 metal sulfate had dissolved in 25.0 cm3 of water.

Use this information and Table 1 in part (b) to identify the Group 2 metal sulfate.

2d3 marks

The uncertainty of the balance that the student used to measure the mass of the pure Group 2 metal sulfate was ± 0.0005 g.

Evaluate the effect that this uncertainty has on the identity of the Group 2 metal sulfate identified in part (c). 

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3a3 marks
i)
Describe the trends in first ionisation energy and atomic radius as you move up Group 2.

ii)
Explain the connection between first ionisation energy and atomic radius.
3b3 marks

Figure 1 shows the melting points of the Group 2 elements. 

Figure 1

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Magnesium does not follow the general trend of the Group 2 metals. The actual melting point of magnesium is around 72.6 % of the expected value. 

Plot the actual melting point of magnesium on Figure 1.

3c4 marks

The Kroll process is used to extract titanium from its ores, commonly rutile (TiO2). The Kroll process involves, first, reacting rutile with chlorine and then reacting the product with magnesium at a temperature of 800 - 900 degreeC. The reaction with magnesium is
exothermic, releasing around 412 kJ mol-1. The final product is a titanium “sponge” which predominantly contains titanium and magnesium chloride.

i)
Identify the role of the magnesium in the reaction.

ii)
Use the information to suggest limitations of this process.

iii)
Suggest how the titanium can be extracted from the sponge.
3d1 mark

Milk of magnesia, Mg(OH)2, can be taken to relieve constipation and, as an antacid, to neutralise excess acid in the gut. It is used because magnesium hydroxide is only sparingly soluble in water so it is not absorbed into the body.

Suggest another property of milk of magnesia that makes it suitable for use in the human body.

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4a1 mark

Many of the Group 2 metal compounds are used to neutralise acid. Calcium hydroxide is used in agriculture to neutralise acidic soil, while magnesium hydroxide is used in medicine to neutralise excess stomach acid.

Write a balanced symbol equation, including state symbols, to represent these reactions.

4b2 marks

Burning fossil fuels releases acidic pollutants into the atmosphere. These acidic gases can be removed from flue gases by a process called wet scrubbing. In wet scrubbing, a slurry is made by mixing powdered lime or limestone with water. This slurry is then sprayed on to the flue gases. One acidic gas reacts with the alkaline slurry to form solid calcium sulfite.

Write two balanced symbol equations, including state symbols, to show the reaction of this acidic gas with the lime slurry and the limestone slurry.

4c1 mark

Barium sulfate is used to diagnose problems within the digestive tract. Patients are advised to not eat or drink for 8 - 12 hours before a barium swallow and can be described as nil-by-mouth. One reason for not eating before the barium swallow is so
that the barium sulfate doesn’t coat any food substances and give a false image of a blockage.

Suggest one reason for not drinking before the barium swallow.

4d4 marks

A technician found a bottle of clear liquid, X, with only part of the label still on the bottle. From the label, the technician determined that liquid X is a solution containing a sodium salt. The technician added barium chloride solution to a small portion of liquid X and
observed a white precipitate. The technician concluded that the solution was sodium sulfate.

i)
Suggest an alternative identity for the unknown sodium salt, X.

ii)
Suggest an improved method with expected observations.

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