AQA Jun 2013 Paper 2 Q1 (with explained solutions) |

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AQA Jun 2013 Paper 2 Q1

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section a answer all questions in the spaces provided do not write outside the box sulfuric acid is manufactured by the contact process a in this process sulfur dioxide reacts with oxygen the equation for the equilibrium that is established is so g o g so g h kj mol a i state and explain the effect of a decrease in temperature on the equilibrium yield of so effect of a decrease in temperature on yield explanation marks extra space a ii give two features of a reaction at equilibrium feature feature marks question continues on the next page turn over wmp jun chem b write an equation for the reaction of concentrated sulfuric acid with potassium bromide to form potassium hydrogensulfate and hydrogen bromide do not write outside the box mark c bromine is one of the products formed when concentrated sulfuric acid reacts with hydrogen bromide write an equation for this reaction state the role of sulfuric acid in this reaction equation role of sulfuric acid marks d concentrated sulfuric acid is used in a two stage process to convert methylpropene into methylpropan ol stage ch c ch h so ch c oso oh ch stage ch c oso oh ch h o ch c oh ch h so d i name and outline a mechanism for stage of this conversion name of mechanism mechanism marks wmp jun chem d ii deduce the type of reaction in stage of this conversion mark d iii state the overall role of sulfuric acid in this conversion mark do not write outside the box turn over for the next question turn over wmp jun chem

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mark scheme general certificate of education a level chemistry unit chemistry in action june comments if m is blank mark on and seek to credit the correct information in the explanation if m is incorrect ce for the clip m depends on a correct statement for m for m the equilibrium shifts moves to release heat or to raise the temperature or to heat up the reaction for m credit for concentration not equal concentrations not concentrations is are the same not amount ignore dynamic and ignore speed ignore closed system it is possible to score both marks under the heading of a single feature question a i mark marking guidance m yield increases goes up gets more m the forward reaction to the right is exothermic or gives out releases heat or the reverse reaction to the left is endothermic or takes in absorbs heat m depends on correct m and must refer to temperature heat the position of equilibrium shifts moves left to right to oppose the decrease in temperature a ii m concentration s of reactants and products remain or stay constant the same m forward rate reverse backward rate mark scheme general certificate of education a level chemistry unit chemistry in action june b kbr h so khso hbr c m so identified m correctly balanced equation would also gain m hbr h so br so h o mark m independently m oxidising agent or electron acceptor or oxidant or to oxidise the bromide ion hbr credit this equation in its ionic form ignore state symbols credit multiples credit m equation in its ionic form ignore state symbols credit multiples not h so on the right hand side m not electron pair acceptor mark scheme general certificate of education a level chemistry unit chemistry in action june d i m electrophilic addition m must show an arrow from the double bond towards the h atom of the h o bond ho on a compound with molecular formula for h so m could be to an h ion and m an independent o h bond break on a compound with molecular formula for h so m must show the breaking of the o h bond on h so m is for the structure of the carbocation m must show an arrow from the lone pair of electrons on the correct oxygen of the negatively charged ion towards the positively charged carbon atom on their carbocation nb the arrows here are double headed m both words required for the mechanism m penalise incorrect partial charges on o h bond and penalise formal charges ignore partial negative charge on the double bond m not hso for m credit as shown or oso h only with the negative charge anywhere on this ion or correctly drawn out with the negative charge placed correctly on oxygen max any of marks for a correct mechanism using the wrong organic reactant or wrong organic product if shown or a primary carbocation penalise once only in any part of the mechanism for a line and two dots to show a bond credit the correct use of sticks for m credit attack on a partially positively charged carbocation structure but penalise m d ii hydrolysis d iii catalyst credit nucleophilic substitution but do not accept any other prefix credit phonetic spelling

Question 1 2 3 4 5 6 7 8 9 10 11

Topics to revise

AQA > Physical chemistry > Equilibrium AS >

1 Dynamic equilibrium and factors affecting equilibrium

AQA > Organic Chemistry > Optical isomerism >

1 Optical isomerism

AQA > Inorganic chemistry > Periodicity AS >

1 Periodicity

AQA > Organic Chemistry > Alkenes AS >

3 Electrophilic addition

AQA > Physical chemistry > Energetics and kinetics AS >

5 Kinetics

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