AQA Jun 2015 Paper 1 Q7 (with explained solutions) |

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AQA Jun 2015 Paper 1 Q7

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section b answer all questions in the spaces provided do not write outside the box a some airbags in cars contain sodium azide nan sodium azide is made by reacting dinitrogen monoxide gas with sodium amide nanh as shown by the equation nanh n o nan naoh nh calculate the mass of sodium amide needed to obtain g of sodium azide assuming there is a yield of sodium azide give your answer to significant figures marks question continues on the next page turn over wmp jun chem do not write outside the box b if a car is involved in a serious collision the sodium azide decomposes to form sodium and nitrogen as shown in the equation nan s na s n g the nitrogen produced then inflates the airbag to a volume of m at a pressure of kpa and temperature of c calculate the minimum mass of sodium azide that must decompose the gas constant r j k mol marks wmp jun chem do not write outside the box c sodium azide is toxic it can be destroyed by reaction with an acidified solution of nitrous acid hno as shown in the equation nan hno hcl n no nacl h o c i a cm volume of the nitrous acid solution was used to destroy completely g of the sodium azide calculate the concentration in mol dm of the nitrous acid used marks c ii nitrous acid decomposes on heating balance the following equation for this reaction hno hno no h o d sodium azide has a high melting point predict the type of bonding in a crystal of sodium azide suggest why its melting point is high mark marks type of bonding reason for high melting point question continues on the next page turn over wmp jun chem

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mark scheme a level chemistry chem june marking guidance mark comments m g would be mass m so moles nan or m moles nan this is m so would be moles nan then m moles nanh moles m mass nanh m or or g allow alternative methods there are process marks mass mass or moles or moles nan moles nanh if or seen to sig figs award marks of question a m k and pa m n pv or rt m or moles n m moles nan m mass nan m g b mark scheme a level chemistry chem june allow only this answer but allow to more than sig figs m is for m m is for moles m allow to g allow answers to sig figs or more of mark scheme a level chemistry chem june moles nan or moles nitrous acid conc or mol dm hno hno no h o ionic oppositely charged ions na and n strong attraction between oppositely charged ions lots of energy needed to overcome strong attractions between ions ions m is for m only this answer can allow multiples if not ionic then ce penalise incorrect ions here but can allow m m dependent on m of c i c ii d e i n n n co n o bef hn e ii e iii mgn mark scheme a level chemistry chem june only allow other correct molecules only of

Question 1 2 3 4 5 6 7

Topics to revise

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