AQA A-level CHEMISTRY (7405/3) Paper 3 Mark scheme June 2023.

AQA A-level CHEMISTRY (7405/3) Paper 3 Mark scheme June 2023. catalyst ALLOW reduces Ea IGNORE speeds up reaction IGNORE provides alternative path IGNORE proton donor IGNORE dehydrating agent 1 Question Answers Additional comments/Guidelines Mark 1.2 electric heater/heat mantle or (hot) water bath IGNORE not with a Bunsen/naked flame / gently ALLOW hot water ALLOW heating/hot plate/ sand bath / oil bath ALLOW reference to flame/Bunsen if in context of heating a water bath NOT any indication of direct heat from Bunsen 1 MARK SCHEME – A-LEVEL CHEMISTRY – 7405/3 – JUNE 2023 12 Question Answers Additional comments/Guidelines Mark 1.3 M1 there is a bung/stopper (in the end of the condenser) M2 idea of pressure build up M3 water goes the wrong way through the condenser M4 water does not fill the condenser / condenser is not cool enough owtte M2 stopper could be forced out IGNORE glass shatters / explodes water in at top / out at bottom IGNORE condenser is wrong way round ALLOW less condensing / vapour/gas/reactants/products will not condense / not as effective at cooling/condensing vapour/reactants/products escapes IGNORE uneven cooling NOT mixture in flask not cooled ALLOW M1/M3 neck of flask not sealed owtte M2/M4 vapour/reactants/products can escape IGNORE references to clamps 4 MARK SCHEME – A-LEVEL CHEMISTRY – 7405/3 – JUNE 2023 13 Question Answers Additional comments/Guidelines Mark 1.4 M1 to neutralise/react with/remove the acid M2 carbon dioxide / gas is produced ALLOW carboxylic/ethanoic and/or sulfuric IGNORE react with/neutralise the distillate/mixture IGNORE to act as a base NOT if incorrect acid named ALLOW effervescence / bubbles / fizzes IGNORE water vapour produced NOT if incorrect gas named IGNORE pressure build up (as in Q) 2 Question Answers Additional comments/Guidelines Mark 1.5 M1 ethyl ethanoate/it is immiscible with / insoluble in water M2 ethyl ethanoate/it is less dense / has lower density (than water) ALLOW water/solution and ethyl ethanoate/it do not mix, OR aqueous and organic layers do not mix ALLOW ethyl ethanoate/it is hydrophobic IGNORE references to polarity / intermolecular forces IGNORE different/low density NOT lighter ALLOW answers for either mark from either part 2 MARK SCHEME – A-LEVEL CHEMISTRY – 7405/3 – JUNE 2023 14 Question Answers Additional comments/Guidelines Mark 1.6 to remove/absorb water / as a drying agent ALLOW reacts with water ALLOW to dry the product/it IGNORE dehydrates NOT reference to crystals forming NOT to dry the reactants NOT to remove soluble impurities