1. 1
   Element Q has the electron configuration 1s²2s²2p⁶3s²3p⁴. Element R has the electron configuration 1s²2s²2p⁶3s²3p⁶4s². When R is heated with Q, a white ionic solid forms.

   (a)

   What is the charge on the ion formed by Q?

   [1 mark]

   • A6+
   • B2−
   • C2+
   • D6−

   (b)

   Which correctly gives the name and formula of the compound formed by R and Q?

   [1 mark]

   • ACalcium sulfide, CaS
   • BCalcium sulfate, CaS
   • CCalcium sulfide, CaS₂
   • DSulfur calcide, SCa

   (c)

   Explain why Q forms a negative ion rather than a positive ion.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A garden centre sells four products whose labels list the main ingredient: ammonium sulfate (lawn fertiliser), potassium nitrate (plant food), calcium phosphate (bone meal) and iron(III) sulfate (moss killer).

   (a)

   What is the formula of calcium phosphate?

   [1 mark]

   • ACaPO₄
   • BCa₂(PO₄)₃
   • CCa₃(PO₄)₂
   • DCa₃P₂

   (b)

   Which name–formula pair is correct?

   [1 mark]

   • AAmmonium sulfate, NH₄SO₄
   • BMagnesium nitrate, MgNO₃
   • CAmmonium phosphate, NH₄PO₄
   • DPotassium nitrate, KNO₃

   (c)

   Deduce the formula of iron(III) sulfate and show that the compound is electrically neutral.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   When 2.43 g of magnesium ribbon is burned in air, the magnesium reacts with oxygen to form magnesium oxide and with nitrogen to form magnesium nitride. A student expected 4.03 g of product if only magnesium oxide formed, but the product has a mass of 3.89 g. Assume all the magnesium reacted and no product was lost.

   (a)

   Deduce the formulas of magnesium oxide and magnesium nitride from the electron configurations of the atoms.

   [3 marks]

   (b)

   Explain, using calculations, why the mass of product is lower than the student expected.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A student tests four white solids, W, X, Y and Z. W melts at 770 °C, does not conduct electricity as a solid but conducts when molten or dissolved in water; it dissolves in water but not in hexane. X melts at 80 °C, does not conduct electricity in any state, is insoluble in water and dissolves in hexane. Y melts at 1710 °C, does not conduct electricity as a solid or when molten, and is insoluble in both water and hexane. Z melts at 2072 °C, does not conduct as a solid but conducts when molten, and is insoluble in both water and hexane. W is potassium chloride and Z is aluminium oxide.

   (a)

   Deduce which of the four solids are ionic, justifying each decision with all the relevant evidence.

   [6 marks]

   (b)

   Deduce the charges on the ions in Z from the electron configurations of aluminium (Z = 13) and oxygen (Z = 8). Explain why Z has a much higher melting point than W, and evaluate the claim that 'all ionic compounds dissolve in water'.

   [6 marks]

   Total for question 4: 12 marks

End of questions