Chemical formulae and naming compoundsIB MYP Chemistry: Subtopic test

1. 1
   A technician in Nairobi is labelling bottles of ionic compounds for a new school chemistry store room. Each label must give the correct name and formula. She works out each formula from the charges on the ions: sodium Na⁺, magnesium Mg²⁺, aluminium Al³⁺, chloride Cl⁻, oxide O²⁻ and sulfate SO₄²⁻.

   (a)

   What is the formula of magnesium chloride?

   [1 mark]

   • AMgCl
   • BMgCl₂
   • CMg₂Cl
   • DMg₂Cl₂

   (b)

   What is the correct name for the compound with the formula Na₂SO₄?

   [1 mark]

   • Asodium sulfide
   • Bdisodium sulfate
   • Csodium sulfate
   • Dsodium sulfur tetroxide

   (c)

   Explain why the formula of aluminium oxide is Al₂O₃.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A company in Spain produces calcium hydroxide to neutralise acidic soil and calcium nitrate to use as a fertiliser. Calcium ions are Ca²⁺, hydroxide ions are OH⁻ and nitrate ions are NO₃⁻.

   (a)

   What is the formula of calcium hydroxide?

   [1 mark]

   • ACa(OH)₂
   • BCaOH
   • CCaOH₂
   • DCa₂OH

   (b)

   What is the name of the compound with the formula Ca(NO₃)₂?

   [1 mark]

   • Acalcium nitride
   • Bcalcium dinitrate
   • Ccalcium nitrogen trioxide
   • Dcalcium nitrate

   (c)

   Explain why the formula of calcium nitrate is written Ca(NO₃)₂ and not CaNO₃.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student looks up the formulae of some ionic compounds in a data book: sodium chloride NaCl, magnesium chloride MgCl₂, aluminium chloride AlCl₃, sodium oxide Na₂O, magnesium oxide MgO and aluminium oxide Al₂O₃. She hypothesises that the formula of an ionic compound can be predicted from the charges on its ions. Sodium ions are Na⁺, magnesium ions are Mg²⁺, aluminium ions are Al³⁺, chloride ions are Cl⁻ and oxide ions are O²⁻.

   (a)

   Describe the pattern in the formulae of the three chlorides in the data, and explain it.

   [3 marks]

   (b)

   Evaluate the student's hypothesis using the data, and predict the formula of aluminium sulfate. Sulfate ions are SO₄²⁻.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A chemical warehouse in Rotterdam stores calcium carbonate for making cement, sodium hydroxide for making soap and carbon dioxide cylinders for fizzy drink manufacture. Staff from many countries read the labels, and some containers still carry old common names such as 'caustic soda' and 'dry ice' beside the systematic names.

   (a)

   Explain how the formulae of calcium carbonate and carbon dioxide are worked out, and why the two formulae show different things. Calcium ions are Ca²⁺ and carbonate ions are CO₃²⁻.

   [6 marks]

   (b)

   Discuss whether all countries should require systematic chemical names and formulae on labels, instead of common names such as 'caustic soda'.

   [6 marks]

   Total for question 4: 12 marks

End of questions