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Question 19N.2.sl.TZ0.3

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Date November 2019 Marks available [Maximum mark: 11] Reference code 19N.2.sl.TZ0.3
Level sl Paper 2 Time zone TZ0
Command term Apply, Determine, Draw, Explain, Formulate, Show, State Question number 3 Adapted from N/A
3.
[Maximum mark: 11]
19N.2.sl.TZ0.3

The following shows some compounds which can be made from ethene, C2H4.

ethene (C2H4) → C2H5Cl → C2H6O → C2H4O

(a)

State the type of reaction which converts ethene into C2H5Cl.

[1]

Markscheme

«electrophilic» addition ✔

NOTE: Do not accept “nucleophilic addition” or “free radical addition”.
Do not accept “halogenation”.

(b)

Write an equation for the reaction of C2H5Cl with aqueous sodium hydroxide to produce a C2H6O compound, showing structural formulas.

[1]

Markscheme

CH3CH2Cl (g) + OH− (aq) → CH3CH2OH (aq) + Cl− (aq)
OR
CH3CH2Cl (g) + NaOH (aq) → CH3CH2OH (aq) + NaCl (aq) ✔

(c(i))

Write an equation for the complete combustion of the organic product in (b).

[1]

Markscheme

C2H6O (g) + 3O2 (g) → 2CO2 (g) + 3H2O (g)
OR
CH3CH2OH (g) + 3O2 (g) → 2CO2 (g) + 3H2O (g) ✔

(c(ii))

Determine the enthalpy of combustion of the organic product in (b), in kJ mol−1, using data from section 11 of the data booklet.

[3]

Markscheme

bonds broken:
5(C–H) + C–C + C–O + O–H + 3(O=O)
OR
5(414«kJ mol−1») + 346«kJ mol−1» + 358«kJ mol−1» + 463«kJ mol−1» + 3(498«kJ mol−1») / 4731 «kJ» ✔


bonds formed:
4(C=O) + 6(O–H)
OR
4(804«kJ mol−1») + 6(463«kJ mol−1») / 5994 «kJ» ✔
«ΔH = bonds broken − bonds formed = 4731 − 5994 =» −1263 «kJ mol−1» ✔

NOTE: Award [3] for correct final answer.

(d(i))

State the reagents and conditions for the conversion of the compound C2H6O, produced in (b), into C2H4O.

[2]

Markscheme

K2Cr2O7/Cr2O72−/«potassium» dichromate «(VI)» AND acidified/H+
OR
«acidified potassium» manganate(VII) / «H+» KMnO4 / «H+» MnO4− ✔

NOTE: Accept “H2SO4” or “H3PO4” for “H+”.
Do not accept “HCl”.
Accept “permanganate” for “manganate(VII)”.

 

distil ✔

 

(d(ii))

Explain why the compound C2H6O, produced in (b), has a higher boiling point than compound C2H4O, produced in d(i).

[2]

Markscheme

C2H6O/ethanol: hydrogen-bonding AND C2H4O/ethanal: no hydrogen-bonding/«only» dipole–dipole forces ✔

hydrogen bonding stronger «than dipole–dipole» ✔

(e)

Ethene is often polymerized. Draw a section of the resulting polymer, showing two repeating units.

[1]

Markscheme

NOTE: Continuation bonds must be shown.
Ignore square brackets and “n”.

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