AQA Jun 2014 Paper 5 Q2 (with explained solutions) |

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AQA Jun 2014 Paper 5 Q2

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table shows some enthalpy change and entropy change data do not write outside the box table h kj mol s j k mol agcl s agcl s agf s ag g ag g cl g ag aq cl aq ag aq f aq ag aq to be calculated a define the term enthalpy of hydration of an ion marks b use data from table to calculate a value for the enthalpy of hydration of the chloride ion marks c suggest why hydration of the chloride ion is an exothermic process marks wmp jun chem d silver chloride is insoluble in water at room temperature do not write outside the box use data from table to calculate the temperature at which the dissolving of silver chloride in water becomes feasible comment on the significance of this temperature value marks calculation of temperature significance of temperature value e when silver fluoride dissolves in water at c the free energy change is kj mol use this information and data from table to calculate a value with units for the entropy change when silver fluoride dissolves in water at c marks turn over wmp jun chem

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mark scheme a level chemistry chem june marking guidance mark comments enthalpy change h when mol of a gaseous ion forms aqueous ions h solution h lattice h hydration or h hydration cl or h hydration cl kj mol enthalpy change for x g x aq scores m and m allow heat energy change instead of enthalpy change allow mol applied to aqueous or gaseous ions if substance atoms in m ce if wrong process eg boiling ce allow any one of these three for m even if one is incorrect allow no units penalise incorrect units allow kj mol allow lower case j for j joules does not score m but look back for correct m of question a b mark scheme a level chemistry chem june water is polar water has h chloride ion attracts the h in water molecules note chloride ion can be implied from the question stem g h t s g so t h s t k allow range to above the boiling point of water therefore too high to be sensible water would evaporate idea that there is a force of attraction between the chloride ion and water do not allow h bonds dipole dipole vdw intermolecular but ignore loose mention of bonding do not allow just chlorine or chlorine atoms ion mark independently look for this equation in d and or e equation can be stated or implied by correct use record the mark in d units essential allow lower case k for k kelvin correct answer with units scores m m and m k scores m and m but not m can only score this mark if m k of c d s h g t or s g h t or j k mol or kj k mol allow to allow to e mark scheme a level chemistry chem june answer with units must be linked to correct m for m units must be correct correct answer with appropriate units scores m m and m and possibly m in d if not already given correct answer without units scores m and m and possibly m in d if not already given answer of means temperature of used instead of so scores m only if ans assume ae and look back to see if m and possibly m are scored of

Question 1 2 3 4 5 6 7 8

Topics to revise

AQA > Physical chemistry > Thermodynamics >

2 Born-Haber cycle

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5 Gibb’s Free Energy

AQA > Physical chemistry > Thermodynamics >

3 Trends in Lattice Enthalpy

AQA > Physical chemistry > Amount of substance AS >

1 The mole and Avogadro’s constant

AQA > Physical chemistry > Energetics and kinetics AS >

2 Calorimetry

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