Chemical formulae and naming compoundsIB MYP Chemistry: Mind map

Exam questions on Chemical formulae and naming compounds

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⁻.
   Explain why the formula of aluminium oxide is Al₂O₃.2 marks
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⁻.
   Explain why the formula of calcium nitrate is written Ca(NO₃)₂ and not CaNO₃.2 marks
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⁻.
   Describe the pattern in the formulae of the three chlorides in the data, and explain it.3 marks