Fuhua 2018 Prelim P2

2 Section A Answer all the questions in the spaces provided. A1 Table A1.1 shows the most common oxidation states of some elements A, B, C, D and E. element most common oxidation states A +1 B +2 C -1 D -2 E +4 Table A1.1 Use the letter(s) to answer the following questions. (a) Which element has a giant molecular structure? [1] (b) Which elements consist of molecules? [1] (c) Which elements conduct electricity in both solid and liquid states? [1] (d) What are the chemical formulae of the oxides of B and C? formula of oxide of B formula of oxide of C [2] (e) No element from Group 0 appear in the table. Use the information in the table to explain why this is true. [2]

3 (f) Draw the dot and cross diagram to show the bonding in the compound formed between the following elements. Show only the outer electrons. (i) B and C [1] (ii) D and E [2] [Total: 10] A2 Graph A2.1 shows the percentage yield of ammonia in the equilibrium mixture under different temperature and pressure conditions. Graph A2.1 temperature / °C yield of ammonia / % 400 atm 200 atm 100 atm 50 atm 25 atm

4 (a) In an industrial Haber process, the operating conditions are at a temperature of 450°C and a pressure of 200 atm. With reference to the graph, state the percentage yield of ammonia under such operating conditions. [1] (b) In industrial Haber process, the yield of ammonia is never 100%. Suggest a reason why. [1] (c) It has been stated that, ‘the use of 450°C is a compromise between the equilibrium yield of ammonia and the rate of reaction’. Explain this statement. [2] (d) The ammonia is separated as a liquid from the unreacted gases. Apart from cost, suggest two other reasons why the unreacted gases are recycled. [2] (e) Calculate the mass, in tonnes, of ammonia which can be produced from 90 tonnes of hydrogen when the percentage yield is 50%. [1 tonne = 1000 kg] [3] [Total: 9]

5 A3 Table A3 .1 shows some data about the names, structural formulae and enthalpy change of combustion of aldehydes. name of aldehydes structural formula boiling point / °C enthalpy change of combustion (kJ/mol) methanal HCHO -19.0 -571 ethanal CH3CHO 20.2 -1170 48.8 -1820 butanal CH3CH2CH2CHO 74.8 -2480 Table A3.1 (a) Use two pieces of evidence in the table to explain why aldehydes are a homologous series. [2] (b) Give the name and structural formula of the third member of this homologous series. name structural formula [2] (c) Calculate the enthalpy change of combustion when 1 g of methanal burns. Show your working.