Edexcel Jun 2015 Paper 1 Q19 (with explained solutions) |

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Edexcel Jun 2015 Paper 1 Q19

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19 Sodium and chlorine react together to produce sodium chloride. The bonding in the product is different from that in both of the reactants. Evidence for the type of bonding present can be obtained in a number of different ways. (a) Draw the electron density map for a chlorine molecule to show covalent bonding. (b) Sodium chloride is ionically bonded. What is meant by the term ionic bond? (1) (1)(c) Electrolysis is an experiment which you could carry out in a school or college laboratory on an aqueous solution of sodium chloride, to provide evidence for the presence of ionic bonding. Draw a labelled diagram of the apparatus that you would use for this experiment, indicating how your results would show that the bonding was ionic. (3) 18 *P44879A01824*<br />
(d) Chlorine gains an electron when it reacts with sodium to form sodium chloride. (i) Draw the dot and cross diagram of a chloride ion showing outer electrons only. (1) (ii) Give the formula of an ion from Period 3 that is isoelectronic with the chloride ion. (1)(e) Sodium and sodium chloride can both be good conductors of electricity. Under what conditions do these substances conduct electricity? Compare the method of conductivity in each case. (3)(Total for Question 19 = 10 marks) *P44879A01924* 19 Turn over<br />

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Question Number 19(a) Acceptable Answers Reject Mark Drawing must have at least 1 circle around each chlorine atom OR Random dots to indicate electron density around both chlorine atoms and a concentrated area between the atoms Acceptable Answers Reject (Electrostatic) attraction between oppositely charged ions IGNORE comments on the formation of ions Mark Question Number 19(b)<br />
Mark Reject Sodium electrode Sodium formed Question Number 19(c) Acceptable Answers Marking point 1 Either Diagram of U-tube / beaker with electrodes and sodium chloride solution OR Diagram of microscope slide with electrodes attached and either filter paper soaked in sodium chloride solution or dampened/wet filter paper on the top of the slide with the sample added (in the centre) (1) Marking point 2 Suitable circuit (1) If electrodes labelledor named they must be consistent with the cell For example the following would not score this marking point: Marking point 3 Ammeter/ light bulb showing conductivity OR Chlorine (gas) evolved/ Test for chlorine/hydrogen (gas) evolved/Test for hydrogen (1) ALLOW any other reasonable electrolysis apparatus that would work to show ionic bonding. For MP3 if the electrode at which the gas is<br />
evolved is stated then it must have the correct sign or charge, although it is not necessary to name or give a sign for the electrode, ie chlorine at the electrode with a positive sign and hydrogen at the electrode with a negative sign. Use of other ionic compounds can only score MP2 Question Number 19(d)(i) Correct dot and cross diagram with charge Acceptable Answers Example XXXX Cl X XX ALLOW all dots or all crosses IGNORE any sodium dot and cross diagram Question Number 19(d)(ii) (Isoelectronic example) S2-/S-2/P3-/P-3 Acceptable Answers Reject Mark Reject Mark Si4-/K+/Ca2+/Ar Sodium in solution/dissolved Mark Acceptable Answers Reject Marking point 1 Sodium conducts when solid (and liquid/molten) (1) Marking point 2 Sodium chloride conducts when molten (and in solution but not as a solid) (1) Marking point 3 Charge carriers in sodium are (delocalised) electrons but ions in sodium chloride OR Conductivity in sodium due to the movement of (delocalised) electrons but the movement of ions in sodium chloride (1) (TOTAL FOR QUESTION 19 = 10 MARKS) Question Number 19(e)<br />

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