Edexcel Jun 2017 Paper 2 Q20

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Answer ALL the questions. Write your answers in the spaces provided. SECTION C 20 Fireworks are designed to explode in a controlled manner with bursts of brightly coloured light and loud bangs. It is believed that fireworks originated in China, after the discovery of gunpowder over 1000 years ago. Fireworks essentially consist of: (cid:404) colour-producing compounds (often metal salts) (cid:404) (cid:404) oxidizer (cid:404) binders (often a type of starch) (cid:404) fuse. fuel In addition, there may be substances known as chlorine donors to strengthen the colour, regulators to control the rate of reaction and reducing agents to produce hot gases. Inside the firework are small globules, called stars, which give fireworks their colour when they explode, for example calcium carbonate is used to produce an orange-red colour. If these stars are arranged randomly, then they will spread out in the sky on explosion. However, if the stars are packed in a regular pattern, then, on explosion, a particular shape can be created in the sky. (a) Give the formulae of two metal carbonates that could be used to produce a bright red colour from an exploding firework. (2)*(b) Explain, by reference to electronic transitions, how the metal ions produce the colours of the firework. (3)16 *P53493A01620* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> (c) Suggest a metal which may be used to produce a white colour in a firework and give the name of the compound produced. (2)(d) Gunpowder is often used in fireworks. It is a mixture of charcoal, sulfur and potassium nitrate. (i) Complete the equation for one of the chemical reactions that occurs when gunpowder burns. (2) KNO3 + S + C (cid:111) K2S + N2 +(ii) Identify two different atoms that have been reduced and state the change in their oxidation numbers. (3) Atom Atom Oxidation number change fromtoOxidation number change fromtoA E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D *P53493A01720* 17 Turn over<br /> (e) In the 1830s, the more explosive oxidizers called chlorates were discovered. One of these is potassium chlorate(VII), KClO4. (i) Suggest how the dot-and-cross diagram for the chlorate(VII) ion may be completed. Use dots () for the chlorine electrons, crosses () for the oxygen electrons and an asterisk(*) for the extra electron on one of the oxygen atoms. (2)Cl (ii) Environmentalists have raised concerns about the use of potassium chlorate(VII) so alternatives are being investigated. Suggest one possible impact on the environment that potassium chlorate(VII) may have. (2)18 *P53493A01820* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> A E R A S I H T N I E T I R W T O N O D *(f) Describe fully how the fuse in a firework starts the chemical reaction and why it is not a catalyst. (3)*(g) Use your knowledge of reaction kinetics to suggest two factors that could affect the rate of reaction of the solids in a firework. Justify your answer. (3) A E R A S I H T N I E T I R W T O N O D A E R A S I H T N(Total for Question 20 = 22 marks) TOTAL FOR SECTION C = 22 MARKS TOTAL FOR PAPER = 80 MARKS I E T I R W T O N O D *P53493A01920* 19<br />

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