Calcium and its compounds have a large variety of applications.

1. (a)(i)Write an equation for the reaction of calcium with dilute nitric acid. State symbols are not required.[1]
2. (a)(ii)When calcium metal is placed in dilute sulfuric acid, it reacts vigorously at first. After a short time, a crust of calcium sulfate forms on the calcium metal and the reaction stops. Some of the calcium metal and dilute sulfuric acid remain unreacted. Suggest an explanation for these observations.[2]
3. (b)(i)Draw the 'dot-and-cross' diagram of the cation present in calcium ethanedioate. Show all electrons.[1]
4. (b)(ii)Draw the displayed formula of the anion present in calcium ethanedioate.[2]
5. (c)(i)Suggest a use for calcium chlorate(I).[1]
6. (c)(ii)The chlorate(I) ion is formed when cold aqueous sodium hydroxide reacts with chlorine. Write an ionic equation for this reaction. State symbols are not required.[1]
7. (c)(iii)The chlorate(I) ion is unstable and decomposes when heated as shown. Deduce the oxidation number of chlorine in each species. Complete the boxes. 3ClO⁻ → 2Cl⁻ + ClO₃⁻ oxidation number of chlorine: +1 [ ] [ ][1]
8. (c)(iv)In terms of electron transfer, state what happens to the chlorine in the reaction in (iii).[1]
9. (d)(i)Identify the two other products of the reaction of lactic acid with calcium carbonate. [Figure 3.1: Structure of lactic acid (2-hydroxypropanoic acid)][1]
10. (d)(ii)Two possible methods of making lactic acid are shown. [Figure 3.2: Reaction schemes for making lactic acid] State suitable reagents and conditions for reactions 1 and 3. reaction | reagents and conditions 1 | 3 | [4]
11. (d)(iii)Name the type of reaction that occurs in reaction 2.[1]
12. (d)(iv)Reaction 4 uses NaBH4. Identify the role of NaBH4 in this reaction.[1]
13. (d)(v)Lactic acid has a chiral centre. State what is meant by the term chiral centre.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.