Trends in Group 2 properties and reactionsAQA A-Level Chemistry: Subtopic test

1. 1
   The first ionisation energies of four Group 2 elements (in kJ mol⁻¹) are: Mg 738, Ca 590, Sr 550, Ba 503.

   (a)

   Which statement explains why the first ionisation energy decreases down Group 2?

   [1 mark]

   • AThe atomic radius and shielding increase, so the outer electrons are attracted less strongly
   • BThe nuclear charge decreases, so the outer electrons are attracted less strongly
   • CThe number of outer electrons increases, so each is held less strongly
   • DThe number of shells decreases, so the outer electrons are further away

   (b)

   Which equation represents the first ionisation of calcium?

   [1 mark]

   • ACa(s) → Ca⁺(g) + e⁻
   • BCa(g) → Ca²⁺(g) + 2e⁻
   • CCa(g) → Ca⁺(g) + e⁻
   • DCa⁺(g) → Ca²⁺(g) + e⁻

   (c)

   Explain why the atomic radius of barium is greater than the atomic radius of calcium.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   The melting points of four Group 2 metals are: Mg 923 K, Ca 1115 K, Sr 1050 K, Ba 1000 K.

   (a)

   What is the structure of a Group 2 metal in the solid state?

   [1 mark]

   • ASimple molecular lattice
   • BGiant ionic lattice
   • CGiant covalent lattice
   • DGiant metallic lattice

   (b)

   How many delocalised electrons does each barium atom contribute to the metallic lattice?

   [1 mark]

   • A1
   • B2
   • C3
   • D4

   (c)

   Explain why barium has a lower melting point than calcium.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A teacher compares the reactions of Group 2 metals with water. Calcium reacts steadily with cold water. Magnesium shows only a few bubbles with cold water but burns brightly in steam.

   (a)

   Write an equation, including state symbols, for the reaction of calcium with cold water. State and explain whether the resulting solution is acidic or alkaline.

   [3 marks]

   (b)

   Write an equation for the reaction of magnesium with steam. Explain why barium reacts with cold water much more vigorously than magnesium.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Titanium metal is made by heating titanium(IV) chloride, TiCl₄, with magnesium at about 1000 K in a sealed reactor filled with argon. The process has a yield of 85%. Relative atomic masses: Ti 47.9, Mg 24.3, Cl 35.5.

   (a)

   Explain how magnesium is used in the extraction of titanium from titanium(IV) chloride. Your answer should include an equation, a reason why magnesium can be used and a reason why argon is used.

   [6 marks]

   (b)

   Calculate the mass of titanium, in kg, obtained from 500 kg of TiCl₄ at 85% yield, and the mass of magnesium, in kg, needed to react with all of the TiCl₄.

   [6 marks]

   Total for question 4: 12 marks

End of questions