Separate samples of 0.01 mol of magnesium nitrate and 0.01 mol of strontium nitrate are heated until completely decomposed to the metal oxide, nitrogen dioxide and oxygen.

1. (a)State which of these two Group 2 nitrates requires the higher temperature before it begins to decompose. Explain your answer.[2]
2. (b)After decomposition is complete the 0.01 mol sample of magnesium oxide is taken and increasing amounts of water are added to it, with stirring, until no solid remains. This procedure is repeated with the 0.01 mol sample of strontium oxide. Identify the sample to which most water must be added to cause all the solid to dissolve. Explain your answer by reference to the solubilities of the products formed when water is added to the oxides. You should refer to relevant energy terms in your answer.[3]
3. (c)(i)The nitrogen dioxide given off by the decomposition of 0.0100 mol of strontium nitrate is dissolved in water. The oxidising agent H₂O₂(aq) is then added to give 150.0 cm³ of a solution in which nitric acid, HNO₃, is the only nitrogen-containing product. Calculate the concentration, in mol dm⁻³, of HNO₃ in the 150.0 cm³ of solution.[1]
4. (c)(ii)The HNO₃ present in 25.0 cm³ of this solution is neutralised using 0.125 mol dm⁻³ NaOH(aq). Calculate the minimum volume, in cm³, of NaOH(aq) needed. Give your answer to three significant figures.[1]