Edexcel Jun 2009 Paper 2 Q21 (with explained solutions) |

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Edexcel Jun 2009 Paper 2 Q21

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PMT 21 The graph below shows the boiling temperatures of the hydrides of Group 7. Boiling temperatures of Group 7 hydrides (a) (i) Identify the type of intermolecular force that gives rise to the unusually high boiling temperature of hydrogen fluoride. (1)(ii) State and explain whether the electronegativity of fluorine is greater than, similar to or less than, that of bromine. Hence explain why hydrogen fluoride can form the type of intermolecular force named in (a)(i) but hydrogen bromide cannot. (3)14 *h34472A01424*<br />
PMT (iii) Use the graph to predict what the boiling temperature of hydrogen fluoride would be without the presence of the type of intermolecular force named in (a)(i). (1)(b) Propanone, CH3COCH3, is a useful solvent for cleaning glassware in laboratories. (i) Why is propanone able to dissolve a wide range of substances? (1)(ii) Propanone can be used to remove both water and octane from glassware. For each of these substances, identify the strongest intermolecular force formed with propanone and the feature of the propanone molecule involved. (2) WaterOctane(Total for Question 21 = 8 marks) *h34472A01524* 15 Turn over<br />

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Question Number 20 (d) Question Number 21 (a)(i) Question Number 21 (a)(ii) Mark Mark Mark Reject Alkali Hydroxide Correct Answer (Slower) as CF bond is stronger (than C-Cl)/fluorine bonds more strongly/fluorine holds the carbon more strongly OR Slower as F is a poorer leaving group (than Cl) (1) Use sodium hydroxide /NaOH/ potassium hydroxide /KOH/ hydroxide ions (1) As OH is a stronger nucleophile / OH has a full negative charge/ more strongly attracted to C+ /OH has more lone pairs (than water)/ OH is more negative than water (1) Correct Answer Reject Hydrogen bonding Hydrogen bond(s) H bonding H bond(s) Notes Accept phonetic/incorrect spelling as long as the word is recognisable Not hydrogen on its own Dipole-dipole bond Permanent dipole-dipole bond Covalent bond van der Waals (forces) Temporary dipole-dipole Induced dipole-dipole London forces Any correct answer in conjunction with an incorrect response, eg hydrogen dipole- dipole bond. Reject Correct Answer (Fluorine atom) is more electronegative (1) Because it has less shielding / (bonding) electrons closer to the nucleus/ smaller /has less shells (so greater pull from nucleus on bonding electrons) (1) so HF has a (greater) dipole moment/H+ on HF (greater than on HBr)/HF is (more) polar (1)<br />
Correct Answer Between 150180 (K) Accept a range within the range e.g. 150-170 Correct Answer Because propanone has both polar and non polar characteristics/can form both London forces and H bonds/can form London forces and dipole-dipole forces OWTTE (1) London forces can be described as Van der Waals VDW Temporary dipole-dipole Instantaneous dipole-induced dipole Correct Answer Water: Hydrogen bonds with the (oxygen of the) carbonyl group/H bonds to the oxygen (1) Octane: London forces with methyl groups/carbon chain/CH groups/ H atoms (1) Both forces given allow (1) Reject C Reject Reject Carbon atoms Correct Answer Use of heat (1) To break down (a reactant)/one reactant into more than one product (1) Correct Answer CaCO3(s)CaO(s) + CO2(g) Allow correct multiples Reject Reject Mark Mark Mark Mark Mark Question Number 21 (a)(iii) Question Number 21 (b)(i) Question Number 21 (b)(ii) Question Number 22 (a)(i) Question Number 22 (a)(ii)<br />

Question 20 21 22 23

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