A-LevelChemistryChemical periodicity9701/22 · Oct/Nov 2018 · Q217 Marks

The table gives some data for elements in the third period and some of their compounds. element Na Mg Al Si P S type of bonding covalent covalent formula of oxide P4O10 SO2 formula of chloride NaCl MgCl2 SCl2

(a)Complete the table to show the bonding in the elements, and the formulae of their oxides and chlorides. element Na Mg Al Si P S type of bonding formula of oxide formula of chloride NaCl MgCl2[3]
(b)(i)SCl2 is formed in the following reaction. S2Cl2(l) + Cl2(g) <=> 2SCl2(l) ΔH = –40.6 kJ mol–1 Complete the ‘dot-and-cross’ diagram to show the bonding in a molecule of SCl2. Show outer electrons only. [Figure showing incomplete dot-and-cross diagram for SCl2][1]
(b)(ii)Complete and fully label the reaction pathway diagram for the reaction between S2Cl2 and Cl2. Include labels for activation energy, Ea, and enthalpy change of the forward reaction, ΔH. [Figure showing incomplete reaction pathway diagram][2]
(c)(i)On the axes, sketch the trend in melting point of the elements Na to S. [Figure showing axes for melting point of element vs Na, Mg, Al, Si, P, S][1]
(c)(ii)Give three statements to explain your sketch.[3]
(d)Write an equation for the reaction of P4O10 with water.[1]
(e)SO2 can be released into the atmosphere when fossil fuels containing sulfur are burnt. State and explain one environmental consequence of the release of SO2 into the atmosphere.[2]
(f)The elements in the third period show a general increase in their first ionisation energies from left to right. Identify two pairs of successive elements in the third period that do not agree with this statement. For each pair, explain why the change in ionisation energy does not agree with this statement. Use of the Data Booklet may help you to answer this question. pair 1 explanation pair 2 explanation[4]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.

[1] Na type of bonding: metallic
[1] Mg type of bonding: metallic
[1] Al type of bonding: metallic
[1] Si type of bonding: covalent
[1] P type of bonding: covalent
[1] S type of bonding: covalent
[1] Na formula of oxide: Na2O
[1] Mg formula of oxide: MgO
[1] Al formula of oxide: Al2O3
[1] Si formula of oxide: SiO2
[1] P formula of oxide: P4O10
[1] S formula of oxide: SO2
[1] Na formula of chloride: NaCl
[1] Mg formula of chloride: MgCl2
[1] Al formula of chloride: AlCl3
[1] Si formula of chloride: SiCl4
[1] P formula of chloride: PCl5
[1] S formula of chloride: SCl2
[1] (diagram showing S with two lone pairs and two single bonds to Cl, each Cl with three lone pairs and one single bond to S)
[1] M1 profile for exothermic reaction
[1] M2 identification of ∆H and Ea
[1] graph rises to maximum for Si, then falls
[3] Max. 3 from: increasing strength of metallic bond; Na < Mg < Al OR stronger attraction between delocalised electrons and (positive) ion so melting point of Na < Mg < Al
[3] Max. 3 from: Si is giant covalent AND it has the highest melting point due to breaking / presence of strong (covalent) bonds OR Si requires the most energy because the covalent bonds in Si are stronger than metallic bonds (in Na / Mg/Al)
[3] Max. 3 from: P and S have weak(er) intermolecular forces / induced dipoles / van der Waals forces (than covalent/metallic bonds) so have low(er) melting points
[3] Max. 3 from: S(8) has stronger / more intermolecular forces / van der Waals forces / induced dipoles than P(4) so melting point of S(8) is higher
[1] P4O10 + 6H2O → 4H3PO4
[1] M1 acid rain
[1] M2 any of the following: lowers pH / increases acidity of rivers / lakes / oceans / water supplies / seas / soil / ground water; kills / harms / damages fish / coral / aquatic life / plants / crops / trees or deforestation; leaches (toxic) aluminium (ions / salts) from soil (into rivers/lakes); leaches away soil nutrients / soil unfit for agriculture; damages / weathers / erodes / destroys buildings / statues; causes breathing difficulties
[1] M1 process of 'first ionisation energy' involves the loss/removal of an electron
[1] M2 Mg and Al AND S and P (in either order)
[1] M3 For Al 3p (orbital / sub-level / sub-shell) is higher in energy / further from the nucleus / more shielded (than Mg) ora
[1] M4 For S the pair of electrons in the (3)p-orbital repel ora