Chemical Tests 1 MS Chemical Tests 1 MS

Chemical Tests 1 MS Chemical Tests 1 MS

• 1.
  Question number Answer Notes Marks 1(a) (i) M1 & M2 – any two from:  does not melt/high melting point  does not colour the flame  inert/unreactive / does not burn/react with oxygen/air 2 (ii) to remove any substance that may affect the colour 1 (iii) difficult to see the colour produced by the substance (under test) Ignore general physical properties of metals, eg boiling point ignore references to removing impurities Allow result/flame for colour Accept flame not hot enough (to vaporise the sample) Accept the temperature is not high enough (to vaporise the sample) Allow flame is (already) coloured 1 (b) (i) (X) M1 – sodium M2 – chloride (Y) M3 – lithium M4 – sulfate Accept symbol in any formula accept Li symbol and SO4 in any formula accept strontium for M3 1 1 1 1 (ii) iron(II) / Fe2+ / Fe+2 / Fe++ accept ferrous ignore iron ion 1 if both name and formula given both must be correct PhysicsAndMathsTutor.com
• 2.
  (c) M1 –add (dilute) acid M2 – test gas/bubbles/carbon dioxide with limewater M3 – limewater turns milky If incorrect gas mentioned, only M1 can be awarded M3 DEP on mention of gas 1 1 1 PhysicsAndMathsTutor.com
• 3.
  Question number Answer Accept RejectMarks 2 (a) magnesium chloride/MgCl2 oxygen/O2 sulfuric (acid)/H2SO4 IGNORE hydrogen sulfate If name and formula given, both must be correct carbon dioxide/CO2 1 1 1 (b) Mg + H2O  MgO + H2 IGNORE state symbols even if incorrect Penalise incorrect symbols and failure to use subscripts 1 (Total marks for Question 2 = 4 marks) PhysicsAndMathsTutor.com
• 4.
  Question number Answer Accept RejectMarks 3 (a) (i) (ii) (iii) Impurities/chemicals/substances may affect the colour/flame IGNORE affect the result/test colour can (easily) be seen (in a non-luminous flame) IGNORE references to temperature yellow/orange/gold(en) a luminous flame may mask the colour any combination of the acceptable colours, e.g. golden-yellow 1 1 1 (b) (i) (ii) (iii) Li+ and Ca2+ M1 − ammonia/NH3 M2 – (water is needed) to form hydroxide ions/OH— M1 – iron(III)/Fe3+ M2 – ammonium/NH4 + If both names and formulae given both must be correct lithium and calcium/Li and Ca to form an alkali/an alkaline solution/ammonium hydroxide to dissolve the ammonia ammonia needs to be aqueous ferric Ca+ etc any other oxidation states/ferrous ammonia 1 1 1 1 1 Total 8 PhysicsAndMathsTutor.com
• 5.
  Question number Answer Notes Marks 4(a) (i (a) (i) ) hydroxide sodium sulfate 1 1 (ii) green precipitate Accept ferrous in place of iron(II) Accept in either order Ignore formulae even if wrong Max 1 if extra product added Ignore oxidation state of sulfate Ignore qualifiers such as pale / dark / dirty Accept solid / suspension / ppt(e) in place of precipitate Ignore grey Reject all other colours Reject bubbles or equivalent Ignore refs to turning brown Ignore refs to reaction type (eg displacement / oxidation) Ignore refs to solution turning colourless / clear Ignore refs to reactants Do not penalise wrong identity or formula of precipitate 1 PhysicsAndMathsTutor.com
• 6.
  1 (ii) 4 (b) (i)barium sulfate / BaSO4 (dilute) hydrochloric acid / HCl 1 fizzing / bubbles / effervescence Accept other suitable acids (name or formula) such as HNO3 / CH3COOH Ignore hydrogen chloride Reject sulfuric acid Reject ‘acid’ alone Reject extra incorrect reagents Allow gas Ignore carbon dioxide Ignore gas tests Ignore wrongly named gas Reject wrong observation (eg precipitate) M2 dep on M1 given Allow M2 if sulfuric acid or just ‘acid’ given in M1 1 PhysicsAndMathsTutor.com
• 7.
  1 M2 1 M3 4 (c)M1 add sodium hydroxide (solution) (and warm) test (gas/ammonia) with (damp red) litmus (paper) OR test with hydrogen chloride / conc. hydrochloric acid turns blue OR white smoke / solid / powder Accept any named Group 1 or Group 2 hydroxide Addition of any other incorrect reagent means 0/3 If no reagent added, max 1 for correct test and result Accept use of universal indicator paper Reject blue litmus for M2 and M3 Ignore ‘ammonium’ Accept HCl Reject dilute hydrochloric acid Do not award M3 if clear statement that litmus is dipped into solution Accept white fumes 1 Total 9 marks PhysicsAndMathsTutor.com
• 8.
  Question number Answer Notes Marks 5a burns with a pop/squeak OR use burning/lit splint/flame to see if pop/squeak Must be reference to test and result Reference to splint/match with no indication of flame is not enough Ignore flame extinguished Reject reference to glowing splint Squeaky pop test on its own is not enough 1 b i 2 anhydrous/white copper sulfate turns blue OR anhydrous/blue cobalt chloride turns pink Ignore colourless Accept correct formula Incorrect formula (eg CuSO) counts as near miss Accept correct formula Incorrect formula (eg CoCl) counts as near miss M2 DEP on M1 or near miss ii measure boiling point / freezing point Accept boil it / freeze it Ignore heat 2 100 (°C) / O (°C) Value must match property Ignore units Answers such as boils/distils at 100 °C / freezes at 0 °C score M2 only PhysicsAndMathsTutor.com
• 9.
  Question number Answer Notes Marks 5b iii If 3 boxes crossed then max 1 If 4 or more boxes crossed then 0 2 cross by carbon dioxide from the air reacts to cause the cloudiness cross by the cloudiness is caused by the formation of a white precipitate Total 7 marks PhysicsAndMathsTutor.com
• 10.
  Question number Answer Notes Marks 6a i M1 1 M2 1 ii bubbles / fizzing / effervescence iron/solid disappears OR green/colourless solution (forms) iron sulfate AND hydrogen (in either order) 1 Accept gas formed /given off Ignore any name or formula Accept iron/solid gets smaller / dissolves Ignore references to heat change / change in pH Penalise oxidation states other than (II) Accept ferrous sulfate Reject ferric sulfate b 2 (1) 2 Accept multiples and fractions 1 c i M1 white 1 M2 blue Ignore colourless Ignore all qualifiers such as pale / dark 1 ii D 1 iii M1 / 1 M2 boiling point 100 ºC melting/freezing point / 0 ºC 1 Accept just º or C but not just number Value must match property Accept correct values in K Ignore other physical properties such as pH / density PhysicsAndMathsTutor.com
• 11.
  Question number Answer Notes Marks 6d i 1 ii low density / less dense than air non-flammable OR does not burn / explode (when ignited) Accept lighter than air / the lightest gas but not just light / lightweight Ignore unreactive Accept does not react with oxygen/air 1 e H2(g) → H2(l) Ignore “+ heat/energy” on RHS Penalise indication of endothermic process 1 Total Tota 12 PhysicsAndMathsTutor.com
• 12.
  Questio n numbe r Answer Notes Marks a 7M1 NH4 + 1 M2 Cl– Award 1 if wrong way around Penalise missing charges both times 1 b i M1 1 M2 1 1 M3 ii M1 1 M2 1 M3 (add) sodium hydroxide/NaOH (solution) (and warm) test (gas / ammonia) with (damp red) litmus (paper) OR test with hydrogen chloride / conc HCl (litmus paper) turns blue OR white smoke/solid/powder (add) silver nitrate/AgNO3 (solution) (dilute) nitric acid white precipitate / solid / suspension Accept any identified Group 1 or Group 2 hydroxide If no reagent added, max 1 mark for correct test AND result even if dipped into solution If just hydroxide or OH- ions, do not award M1 but continue marking If any other incorrect reagent added, then 0/3 Accept use of universal indicator Accept holding litmus above tube etc Reject blue litmus for M2 and M3 Do not penalise ammonium instead of ammonia in M2 Do not allow (dilute) hydrochloric acid Do not award M3 if litmus dipped into solution (even if only implied) If missing or incorrect reagent, 0/3 Do not accept any other acid or just acidified If acid missing or wrong, M3 can still be awarded If bleaching litmus paper mentioned, only M1 can be awarded 1 PhysicsAndMathsTutor.com
• 13.
  Questio n numbe r Answer Notes Marks 7c M1 reversible / goes both ways Ignore equilibrium 1 d i M1 1 ii M1 ammonium chloride / NH4Cl ammonia / NH3 / molecules / they / it are / move / diffuse /travel faster / quicker Do not accept ammonia chloride If name and formula given, both must be correct Ignore descriptions such as lighter / smaller / denser Accept phonetic spellings including amonia / ammonium Do not accept hydrogen chloride / hydrochloric acid / HCl / ammonium chloride / NH4Cl in place of ammonia Accept all other words with same meaning as faster - eg speedier Do not accept react faster or travel further Accept reverse statements such as hydrogen chloride slower 1 e M1 1 M2 Corrosive / burns / damages skin or eyes Wear eye protection eg goggles or mask / gloves / place bung in the end of the tube / use of fume cupboard Ignore harmful / irritant / toxic / poisonous Allow tongs / tweezers if reference to cotton wool Ignore lab coats M1 and M2 are independent 1 Total 13 marks PhysicsAndMathsTutor.com