AQA June 2012 – Unit 5 Q1

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section a answer all questions in the spaces provided do not write outside the box white phosphorus p is a hazardous form of the element it is stored under water a suggest why white phosphorus is stored under water mark b phosphorus v oxide is known as phosphorus pentoxide suggest why it is usually represented by p o rather than by p o mark c explain why phosphorus v oxide has a higher melting point than sulfur vi oxide marks d write an equation for the reaction of p o with water to form phosphoric v acid give the approximate ph of the final solution equation ph marks wmp jun chem do not write outside the box e a waste water tank was contaminated by p o the resulting phosphoric v acid solution was neutralised using an excess of magnesium oxide the mixture produced was then disposed of in a lake e i write an equation for the reaction between phosphoric v acid and magnesium oxide mark e ii explain why an excess of magnesium oxide can be used for this neutralisation mark e iii explain why the use of an excess of sodium hydroxide to neutralise the phosphoric v acid solution might lead to environmental problems in the lake mark turn over for the next question turn over wmp jun chem

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