O-LevelChemistryElectrolysis5070/21 · May/June 2017 · Q47 Marks
Calcium chloride, CaCl₂, is an ionic compound.
- (a)State the electronic configuration for each of the ions in calcium chloride. calcium ion .......................................................................................... chloride ion ..........................................................................................[2]
- (b)When molten calcium chloride is electrolysed, calcium and chlorine are formed. Construct equations for the two electrode reactions. reaction at the negative electrode ................................................................ reaction at the positive electrode .................................................................[2]
- (c)Predict the products of the electrolysis of concentrated aqueous calcium chloride.[1]
- (d)Explain, using ideas about structure and bonding, why calcium chloride has a high melting point.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- A4(a) Calcium ion is 2.8.8 (1)
- Chloride ion is 2.8.8 (1)
- A4(b) Negative electrode: Ca2+ + 2e- Ca (1)
- Positive electrode: 2Cl- Cl2 + 2e- (1)
- A4(c) Hydrogen / H2 AND chlorine / Cl2 (1)
- A4(d) Ionic bonds / attraction between positive ions and negative ions (1)
- Idea of having many (strong) bonds – this mark is dependent on the correct bonding (1)
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