magnesium Mg each horizontal line correct (1) [3] correct direction from zinc to lead (1)

Transcription

1 1 (a (i) aqueous solution lead Pb magnesium Mg zinc Zn silver Ag lead (II) magnesium zinc silver(i) X each hizontal line crect (1) [3] (ii) Zn (1) An arrow from Zn to Zn 2+ (1) (iii) Zn + 2Ag + Zn Ag (1) (b) crect direction from zinc to lead (1) (ii) metals react by losing electrons (1) the me reactive metal / zinc will lose electrons me readily (making the electrode negatively charged). (1) (iii) manganese and zinc are me reactive than lead (and / copper) (1) lead is me reactive than copper (1) (iv) the polarity of a Mn / Zn (cell) the voltages of Zn / Pb and Mn / Pb (cells) (1) [Total: 12]

2 2 (a (i) measure melting point NOT just heating pure sample would melt at 135 C [1 OR impure would melt lower than 135 C (ii) C 3 H 4 O 4 (iii) C 2 H 4 O 2 OR CH 3 COOH ethanoic OR acetic acid both marks are independent of each other (iv) ester NOT ganic, covalent (b) (i) malonic is a weaker acid/less dissociated OR sulfuric acid is a stronger acid/me dissociated NOT sulfuric acid is a strong acid (ii) add piece of suitable metal, e.g. Mg ALLOW Al, Ca NOT K, Na, Cu sulfuric acid reacts faster OR malonic reacts slower OR as above add a piece of CaCO 3, if soluble carbonate then only OR measure electrical conductivity sulfuric acid is the better conduct OR malonic acid poer conduct NOT sulfuric acid is a good conduct (c) (i) sodium malonate and water (ii) CuSO 4 H 2 O (iii) CH 2 (COO) 2 Mg H 2 (iv) K 2 SO 4 CO 2 and H 2 O NOT H 2 CO 3 [Total: 16]

3 3 (a because they have me than one oxidation state valency / fm ions with different charges there are two iron oxides (iron(iii) oxide and iron(ii) oxide) / iron fms Fe 2+ and Fe 3+ compounds / iron fms iron(ii) and iron(iii) compounds (b) (i) to remove the precipitate / remove the silver(i) chromate(vi) / remove the residue (ii) to remove soluble impurities / remove named soluble salt e.g. potassium / remove reactants (iii) to dry solid / to remove water (c) (i) need one mole of potassium chromate(vi) f two moles of silver(i) / crect references to mole ratio (ii) mass of AgNO 3 needed is = 3.4g NOTE: if answer given is 34 they have omitted 0.1 ALLOW: (1) ecf (iii) number of moles of AgNO 3 used = = number of moles of Ag 2 CrO 4 fmed = mass of one mole of Ag 2 CrO 4 = 332g mass of Ag 2 CrO 4 fmed = 0.664g NOTE: use ecf when appropriate [Total: 11]

4 4 (a nitric acid; sodium hydroxide / carbonate / hydrogen carbonate; copper(ii) oxide / hydroxide / carbonate; any named soluble chlide; accept: hydrochlic acid / hydrogen chlide silver(i) / ethanoate / sulfate; must be soluble silver salt not silver oxide / carbonate zinc(ii) sulfate (b) (i) Ag + (aq) + Cl (aq) AgCl(s) equation crect state symbols missing (ii) ZnCO 3 + H 2 SO 4 ZnSO 4 + CO 2 + H 2 O [2 crect fmula f zinc sulfate = 1 [Total: 10] 5 (a (i) A C D B (ii) speed ( rate) increases as concentration increases / time decreases as concentration increases; rate speed time depends on (concentration) of H + hydrogen ions; B is slow because propanoic acid is weak doesn t dissociate weakly ionises; B is slow because HCl and H 2 SO 4 are stronger ionise dissociate me than propanoic; D slower than C because C is me concentrated than D / ORA; A is fast because H + concentration high (note: this would also sce second mark if not already awarded) / H 2 SO 4 is diprotic dibasic 2H + ; time is inversely proptional to rate / owtte / ORA; max [5] (b) change 1: increase temperature / heat (the mixture); particles/molecules/ions have me energy move faster; me (successful) collisions / me particles with E a ; change 2: increase surface area / decrease particle size / use powdered (magnesium) / use smaller pieces / crush the magnesium; me collisions / me particles exposed to reaction; catalyst; me (successful) collisions; lowers E a ; max [5]

5 6 (a) proton don; (b) equal concentrations of both (solutions); add Universal indicat / determine ph / ph paper; ethylamine has lower ph / ORA; equal concentration of both (solutions); measure conductivity of aqueous ethylamine and sodium hydroxide; ethylamine will have lower conductivity / sodium hydroxide will have higher conductivity; (c) add strong(er) base / NaOH / KOH; warm / heat; (d) (ethylamine fms) hydroxide ions / OH (in water); hydroxide ions / OH reacts with iron(iii) ions / Fe 3+ ; iron(iii) hydroxide / Fe(OH) 3 (fms as a brown precipitate); note: balanced unbalanced ionic equation i.e. Fe 3+ + (3)OH Fe(OH) 3 sces both marks