Edexcel Jan 2014 (IAL) Paper 2 Q22

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22 The thermit reaction is a classic chemical demonstration. It is also a chemical reaction which has a number of important industrial uses. (a) The thermit reaction is between iron(III) oxide and aluminium powder and produces aluminium oxide and iron. Complete the balanced equation. State symbols are not required. Fe2O3 + 2Al (cid:111)+(b) For the thermit reaction to work successfully, the iron(III) oxide and aluminium must be mixed in the correct stoichiometric ratio. Calculate the mass of aluminium that would be required to react with 34.0 g of iron(III) oxide. (c) The iron(III) oxide needs to be dried before it can be used in the thermit reaction. Suggest how this could be carried out. (1) (3) (1)(d) The iron(III) oxide and aluminium must be thoroughly mixed. Suggest why this is essential for the reaction to work. (1)12 *P42987A01220*<br /> (e) The thermit reaction requires a source of ignition in order to start. This source needs to generate a lot of heat. Simply heating to red-heat is insufficient, as heating to white-heat is necessary. Often a strip of magnesium ribbon is used as a fuse to ignite the thermit mixture. (i) What would be seen when the magnesium ribbon is first lit? (1)(ii) What is the chemical product of this reaction? (1)(iii) The lighting of the magnesium fuse creates enough heat energy to initiate the thermit reaction. Draw a fully labelled reaction profile diagram for the thermit reaction. The enthalpy change for this reaction is 825 kJ mol1. (iv) Use your reaction profile to explain the role of the magnesium fuse in initiating the thermit reaction. (4) (1)*P42987A01320* 13 Turn over<br /> (v) Explain why the magnesium fuse is not acting as a catalyst for the reaction. (1)(vi) Only a small quantity of magnesium is required to start the reaction. Suggest why this is the case. (1)(f) Occasionally, the thermit mixture can fail to ignite. Suggest why extreme caution should be exercised under such a situation. (1)(g) One industrial application of the thermit reaction is the welding, or the joining, of railway lines. How does the thermit reaction achieve this function? (1)(h) Many alternative chemicals can be used in a thermit-type of reaction. In principle, other reactive metals could be used in place of aluminium, but this is rarely the case in real-life situations. Suggest why. (1)(Total for Question 22 = 18 marks) TOTAL FOR SECTION B = 37 MARKS 14 *P42987A01420*<br />

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