AQA Jun 2012 Paper 1 Q5

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section b answer all questions in the spaces provided do not write outside the box a boron trichloride bcl can be prepared as shown by the following equation b o s c s cl g bcl g co g a sample of boron oxide b o was reacted completely with carbon and chlorine the two gases produced occupied a total volume of cm at a pressure of kpa and a temperature of k calculate the mass of boron oxide that reacted give your answer to significant figures the gas constant r j k mol marks extra space wmp jun chem do not write outside the box b boron trichloride can also be prepared from its elements write an equation for this reaction explain why boron trichloride has a trigonal planar shape with equal bond angles marks extra space c i boron trichloride is easily hydrolysed to form two different acids as shown in the following equation bcl g h o i h bo aq hcl aq calculate the concentration in mol dm of hydrochloric acid produced when g of boron trichloride are added to water to form cm of solution give your answer to significant figures marks extra space c ii boric acid h bo can react with sodium hydroxide to form sodium borate and water write an equation for this reaction mark question continues on the next page turn over wmp jun chem do not write outside the box d boron trichloride can be reduced by using hydrogen to form pure boron bcl g h g b s hcl g calculate the percentage atom economy for the formation of boron in this reaction apart from changing the reaction conditions suggest one way a company producing pure boron could increase its profits from this reaction marks extra space e a different compound of boron and chlorine has a relative molecular mass of and contains of boron by mass calculate the molecular formula of this compound show your working marks extra space copyright aqa and its licensors all rights reserved end of questions wmp jun chem

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