Edexcel Jan 2017 (IAL) Paper 3 Q1 (with explained solutions) |

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Edexcel Jan 2017 (IAL) Paper 3 Q1

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Answer ALL the questions. Write your answers in the spaces provided. 1 A student carried out the tests described to distinguish between the pairs of compounds named in parts (a) to (d). State what you would see when the test is carried out. Identify by name or formula any gases evolved during the reactions in parts (b) to (d). (a) Solid potassium chloride and solid sodium chloride. Test: A flame test. (2) Observation with potassium chlorideObservation with sodium chloride(b) Aqueous potassium sulfate and aqueous potassium carbonate. Test: Addition of excess dilute hydrochloric acid followed by aqueous barium chloride. Identify any gas evolved. (2) Observation with potassium sulfateObservation with potassium carbonate(c) Solid ammonium sulfate and solid potassium sulfate. Test: Warm the solid with aqueous sodium hydroxide and use damp red litmus paper to test any gas released. Identify any gas evolved. (3) Observation with ammonium sulfateObservation with potassium sulfate*P48371A0216*<br />
(d) Solid sodium chloride and solid sodium bromide. Test: Add concentrated sulfuric acid. Identify all of the gases evolved. (4) Observation with sodium chlorideObservation with sodium bromide(Total for Question 1 = 11 marks) *P48371A0316* Turn over<br />

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Mark Correct Answer Reject (Observation with potassium chloride) lilac / purple / mauve / violet Chlorine gas in addition but only penalise once Any red (Observation with sodium chloride) yellow / orange (1) (1) IGNORE Qualifiers such as bright / pale / persistent Question Number 1(a)<br />
For 1(d) Mark the gases separately from the observations. Deduct a mark for incorrect information, eg in (d) hydrogen chloride and hydrogen would not score M1 (+11 = 0) but hydrogen bromide, bromine and hydrogen sulfide would score M3. (+21 = 1) Question Number 1(b) Mark 2 Reject Just turns white Any bubbles / any named gas / any gas released Any precipitate Correct Answer (Observation with potassium sulfate) white precipitate / ppt ALLOW white solid / white crystals IGNORE names of precipitate even if incorrect (1) (Observation with potassium carbonate) fizzing / bubbles / effervescence / turns limewater cloudy AND carbon dioxide / CO2 IGNORE References to NO white precipitate / NO white solid / NO white crystals (1) Correct Answer Reject Mark (Observation with ammonium sulfate) (red litmus paper turns) blue STAND ALONE MARK (due to formation of) ammonia / NH3 (1) (1) Question Number 1(c) White smoke/ any precipitate Ammonium / NH4 SO2/gas evolved/bubbl es/ effervescence / any precipitate (Observation with potassium sulfate) No change / no reaction / no observation /litmus paper remains red / no gas evolved / no ammonia / no NH3 / nothing IGNORE temperature change / dissolves (1)<br />
Correct Answer Reject Mark (1) Mark observations and gases independently (Observation with sodium chloride) M1: hydrogen chloride / HCl M2: Misty / steamy / white fumes OR white smoke with ammonia OR damp blue litmus paper red IGNORE Effervescence throughout (Observation with sodium bromide) M3: Bromine / Br2 (1) (1) Chlorine / sulfur dioxide Just white smoke Yellow / green gas Any additional incorrect products e.g. H2S / S Just Red fumes/gas Coloured fumes eg creamy Hydrogen sulfide / H2S M4: brown (fumes) / orange (fumes) ALLOW Red as a qualifier or red qualified by brown or orange, eg red-brown, orange-red (1) OR M3: hydrogen bromide / HBr (1) M4: Misty / steamy / white fumes OR white smoke with ammonia OR damp blue litmus paper red (1) OR M3: SO2 / sulfur dioxide M4: (acidified) K2Cr2O7 from orange to green / damp blue litmus paper red (1) (1) (Total for Question 1 = 11 marks) Question Number 1(d)<br />

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