11983.05R [Turn over 9 One molecule of cuprimine contains one sulfur atom. The percentage, by mass, of sulfur in cuprimine is 21.47%. The relative molecular mass of cuprimine is A 85. B 101. C 125. D 149. 10 The general formula of an alkyl group is A CnHn + 1 B CnHn − 1 C CnH2n + 1 D CnH2n − 1 11983.05R Section B Answer all four questions in this section 11 Group II metal nitrates are formed when either the metal, the metal oxide or the metal carbonate are reacted with nitric acid. Metal nitrates are very soluble in water and all of the reactions proceed normally, apart from magnesium with nitric acid, because nitric acid is an oxidising agent and causes other reactions to take place. (a) Write equations for the reactions of calcium, calcium oxide and calcium carbonate with dilute nitric acid. (i) calcium: [1] (ii) calcium oxide: [1] (iii) calcium carbonate: [1] (b) Magnesium does not react with most concentrations of nitric acid to give hydrogen. Instead, nitrogen(IV) oxide together with magnesium nitrate and water are produced. Write the equation for the reaction. [1] 11983.05R [Turn over (c) Group II metal nitrates increase in thermal stability as the Group is descended. (i) Explain what is meant by the term thermal stability. [1] (ii) Explain why thermal stability increases down the Group. [1] (d) When heated, the Group II nitrates, M(NO3)2, decompose according to the following equation: 2M(NO3)2 → 2MO + 4NO2 + O2 (i) Explain why the residue left after the reaction gives an alkaline solution when dissolved in water. [1] (ii) If 3.6 g of strontium nitrate is heated and completely decomposes, what is the total volume of gases collected at 20 °C and a pressure of one atmosphere? [3] 11983.05R (iii) The diagram below shows the gases from the decomposition of a nitrate passing through Universal Indicator (UI) solution and one gas being collected in a test tube. Explain why the UI solution goes red and name the gas collected in the test tube. test tube heat UI solution [2] 11983.05R [Turn over (e) Group II metal nitrates are soluble in water. The solubility curve for the Group I nitrate, rubidium nitrate, is shown below. 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 90 100 temperature/°C solubility/ g/100 g water The following data refers to the solubility of strontium nitrate with temperature. Solubility/ g/100 g water 40  55  71  88  91  93  94  97  99  101 Temperature/°C 0  10  20  30  40  50  60  70  80    90 (i) Plot the solubility curve for strontium nitrate on the axes above. [1] (ii) Determine the temperature at which rubidium nitrate and strontium nitrate have the same solubility. [1]