Group 2 (OCR A Level Chemistry A): Exam Questions

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.

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.

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. 

The student had added the exact amount of calcium required to react with the hydrochloric acid used. After carrying out the experiment, the student accidentally added some more calcium. The student was surprised that the extra calcium still reacted.

Explain this observation. Include an equation in your answer.  

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

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

Explain your answer. 

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.

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

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.

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 use of each of the hydroxides. 

Group 2 elements will react with water.

A student added 20 cm³ 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.

The element strontium forms a nitrate, Sr(NO₃)₂, which decomposes on heating as shown below.

2Sr(NO₃)₂ (s) → 2SrO (s) + 4NO₂ (g) + O₂ (g)

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

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.

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

A student watches a demonstration in which strontium is added to water.

The equation for the reaction is shown below.

Sr (s) + 2H₂O (l) → Sr(OH)₂ (aq) + H₂ (g)

In terms of electron transfer, explain why strontium has been oxidised.

Suggest two compounds which could be reacted together to produce Sr(OH)₂.

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. 

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

A student reacts a Group 2 metal, M, with water.

M (s) + 2H₂O (l)→ M(OH)₂ (aq) + H₂ (g)

The student measures the volume of hydrogen gas produced. 0.162 g of the metal produces 97.0 cm³ of gas measured at room temperature and pressure.

Identify the Group 2 metal, M. Show your working.

The student plans to repeat the experiment using the same mass of group 2 metal from further down the group.

Predict whether the volume of hydrogen produced would be greater than, less than or the same as the volume of the first experiment.

Explain your answer.

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. 

A student heats 4.46 g of the Mg(NO₃)₂ and collects the gas at room temperature and pressure, RTP. 

Calculate the volume of gas, in dm³, obtained by the student at RTP.

The values for the first, second and third ionisation energies of magnesium are shown in the table below.

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]

Magnesium hydroxide or 'milk of magnesia' is used in indigestion tablets to neutralise stomach acid. 

Write an ionic equation to demonstrate this reaction. 

Include state symbols.

This question is about Group 2 elements. 

Barium is silvery white but blackens when exposed to air.

This is due to the formation of barium nitride and one other compound.

Write a balanced symbol equation for the two separate reactions which occur. 

Include state symbols. 

Barium can also react with water.

A student reacted 0.20 g of barium with 250 cm³ of water. 

i) Calculate the volume of gas, in cm³,  produced in this reaction under standard temperature and pressure. 

ii) Calculate the concentration, in mol dm^-3 of the barium hydroxide solution produced.

Describe and explain the trend in the reactivity of Group 2 elements with water. 

Explain why the reaction of calcium with water is a redox reaction. 

Use oxidation numbers in your answer.

The trend in solubility and strength as a base can also be observed going down Group 2. 

Explain how these two trends are connected. 

This question is about the reactions of Group 2 metals with acids. 

Group 2 metals react with dilute acids to form metal salts. 

Compare the reaction between strontium and dilute hydrochloric acid with strontium and dilute sulfuric acid.

Include a balanced symbol equation for each reaction with state symbols.

Explain why the reaction between calcium and hydrochloric acid is a redox reaction. 

Use oxidation numbers and half equations in your answer. 

A student prepared a sample of calcium chloride. They added the exact amount of calcium so that all of the HCl had reacted. They used 50 cm³ of 2.0 mol dm^-3 HCl. 

Calculate the mass of calcium that was used. 

Group 2 chlorides all exhibit ionic bonding except berylium chloride. 

Explain how the bonding in berylium chloride differs from the rest of the Group 2 chlorides. 

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.

The table below shows the solubility data for the Group 2 metal hydroxides.

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.

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

i) Write a balanced symbol equation for the reaction. Include state symbols.

[1]

ii) Describe the properties of magnesium hydroxide that make it suitable for use in the human body.

[2]

Calcium hydroxide is added to fields as lime by farmers to increase the pH of acidic soils. 

Give two reasons why calcium hydroxide is used instead of magnesium hydroxide.