AQA Jan 2012 Paper 4 Q3 (with explained solutions) |

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AQA Jan 2012 Paper 4 Q3

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do not write outside the box ammonia and ethylamine are examples of weak br nsted lowry bases a state the meaning of the term br nsted lowry base mark b i write an equation for the reaction of ethylamine ch ch nh with water to form a weakly alkaline solution mark b ii in terms of this reaction state why the solution formed is weakly alkaline mark c state which is the stronger base ammonia or ethylamine explain your answer stronger base explanation marks extra space wmp jan chem do not write outside the box d give the formula of an organic compound that forms an alkaline buffer solution when added to a solution of ethylamine mark e explain qualitatively how the buffer solution in part d maintains an almost constant ph when a small amount of hydrochloric acid is added to it marks extra space turn over for the next question turn over wmp jan chem

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mark scheme general certificate of education a level chemistry unit kinetics equilibria and organic chemistry january question a proton acceptor marking guidance b i ch ch nh h o ch ch nh oh b ii mark independently of b i reaction equilibrium lies to left or low oh or little oh formed or little ethylamine has reacted c ethylamine alkyl group is electron releasing donating or alkyl group has positive inductive effect increases electron density on n h or increased availability of lp or increases ability of lp to accept h m m m mark comments allow eq with or without plus can be on n or h allow c h nh and c h nh or allow rhs as c h nh oh allow ethylamine is only partly slightly dissociated or ethylamine is only partly slightly ionized ignore not fully dissociated or not fully ionized ignore reference to ionisation or dissociation of water if wrong no marks in c mark m is independent of m d e mark scheme general certificate of education a level chemistry unit kinetics equilibria and organic chemistry january ch ch nh cl allow name ethylammonium chloride or ethylamine hydrochloride or other halide for cl mark independently of d extra h reacts with ethylamine or oh or ch ch nh h ch ch nh or h oh h o equilibrium shifts to rhs or ratio ch ch nh ch ch nh remains almost constant or any amine hydrochloride or a strong organic acid not nh cl or makes reference to equilibrium in b i with amine on lhs

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

Topics to revise

AQA > Organic Chemistry > Amines >

2 Base properties

AQA > Physical chemistry > Acid base equilibria >

3 Weak acids

AQA > Physical chemistry > Acid base equilibria >

6 Buffer solutions

AQA > Physical chemistry > Atomic structure AS >

4 Electronic arrangement

AQA > Physical chemistry > Acid base equilibria >

1 Bronsted-Lowry theory and pH

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