Acceptable Answers Reject Mark. Add hydrochloric acid / HCl(aq) / nitric acid / HNO 3 (aq)

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Garry Palmer
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1 (a)(i) Add hydrochloric acid / HCl(aq) / nitric acid / HNO (aq) Just acid only if a suitable acid is given in equation one Sulfuric acid / H SO 4 ((aq)) or HCl Just acid heating the carbonate IGNE conc Gas / carbon dioxide / CO evolved turns lime water milky / cloudy / produces a white precipitate MP is a stand alone mark but there must be some indication that a gas is being tested (a)(ii) i i) ALL H CO (aq) for H O(l) + CO (g) BaCO (s) + HCl(aq) BaCl (aq) + H O(l) + CO (g) BaCO (s) + HNO (aq) Ba(NO ) (aq) + H O(l) + CO (g) CO (s) + H + (aq) H O(l) + CO (g) BaCO (s) + H SO 4 (aq) BaSO 4 (s/aq) + H O(l) + CO (g) BaCO (s) BaO(s) + CO (g) Ca(OH) (aq) + CO (g) CaCO (s) + H O(l) All state symbols in both equations correct State symbols mark if first equation not balanced but ALL species are correct. No TE on other equations

2 (b)(i) MP and MP Dip (clean) nichrome / platinum wire loop / rod for wire Silica rod Nickel / chrome / chromium spatula in hydrochloric acid / HCl(aq) any mention of HCl(aq) e.g. cleaning or mixing solid and acid HCl for HCl(aq) Other acids (for MP and MP) (Wooden) splint Soaked in distilled / deionised water MP then dipped in solid and placed in (hot / roaring / blue-cone) (Bunsen) flame On / over / under / above for in IGNE inoculating / flame-test (wire) just water (b)(ii) A = Mg + B = Ca + Penalise omission of + only once Correct ions with correct charge but the wrong way round scores mark Correct ions with incorrect / no charge scores IGNE Names / compounds

3 (b)*(iii) Read the whole answer before awarding marks. If no mention of electrons only MP may be awarded. Electrons promoted to higher energy level (by thermal energy / heat from (Bunsen) flame) (Promoted) electrons fall / drop / relax to lower energy level / orbital / shell / subshell Electrons return to ground state Emitting radiation / light / photons (in the visible region) Just electrons promoted/ excited Just energy lost Just energy given out IGNE Colour (b)(iv) Emitted radiation is not in the visible region (of the spectrum) Emitted radiation is in IR / UV

4 (c) As group is descended... First mark (metal ion size) (Metal) ion radius increases / has more (electron) shells (but charge remains the same) Charge density of metal ion decreases (Metal) atomic radius increases / has more (electron) shells Second mark (polarizing species) Polarizing ( distorting) power of cation / metal ion decreases Third mark (polarized species) Polarization / distortion of (electron cloud of) carbonate ion /anion decreases Just metal Just ion Just ion or bond C O / C O for carbonate ion (so carbonate more stable to heat) reverse argument for ascent of the group. Total for = 7 marks

5 (a) The outer electrons are closer to the nucleus/smaller Ionic atomic radius/ less electron shells (in calcium) radius/ Molecules Just less electrons Less shielding (in calcium) Reverse argument for strontium Ignore reference to repulsion between shells (b)(i) Nichrome wire / platinum wire / silica rods Nickel/Ni/ Chromium/Cr/ Metal loop/wire (Dip / clean) in (concentrated) HCl/HCl(aq)/dilute HCl and place in Bunsen flame Yellow flame/burn Allow alternative procedures such as: Make a salt solution Soak in wooden splint and place in Bunsen flame (b)(ii) (Pale/Light) green / apple green Blue-green

6 (b)(iii) Electrons promoted to higher energy level Electron(s) return to lower energy level Release of (visible/ light) energy/ photon upon return Proton (c)(i) Barium hydroxide / Ba(OH) Allow product as part of the equation: Ba + H O Ba(OH) + H (c)(ii) Bubbles / Fizzing / Effervescence The metal sinks Air bubbles IGNE The Barium dissolves / forms a colourless solution Increase in temperature Just a gas is produced (d)(i) Barium is oxidized from 0 to + Chlorine is reduced from 0 to - Allow one mark if oxidized and reduced are the wrong way round Ignore reference to transfer of electron unless incorrect. (d)(ii) Ba + (aq) + SO 4 - (aq) BaSO 4 (s) One mark for chemical symbols One mark for state symbols BaSO 4 (aq) Allow one mark maximum for: BaCl (aq)+ H SO 4 (aq) BaSO 4 (s)+ HCl(aq) Ions not cancelled

7 (d)(iii) To prevent formation of carbonate / sulfite / sulfate(iv) (precipitate) / to remove carbonate / sulfite / sulfate(iv) ions Just to remove other ions (e)(i) MgCO + HCl MgCl + H O + CO Ignore state symbols even if incorrect MgCO + HCl MgCl + H CO

8 (e)(ii) Marking Point (Factor) Use larger lumps 4 Marking Point (Explanation) Decreases surface area Fewer collisions between the reactants Alternatively Marking Point (Factor) Decreases surface area Marking Point (Explanation) Fewer collisions between the reactants Marking Point (Factor) Decrease concentration (of acid) Just increased size of MgCO Marking Point 4 (Explanation) Fewer collisions between the reactants Fewer particles for the same volume Explanation marking point only awarded for correct factor or a near miss. Just change in volume of acid (f) Pressure only affects gaseous reactions/ There is no significant volume change/the liquids are incompressible

9 (a)(i) A hydrocarbon (solvent) / volasil / named hydrocarbon solvent / tetrachloromethane Formulae Ethanol Alkenes (a)(ii) Red / brown /orange / amber / yellow Or any combination No TE on incorrect / no reagent (b)(i) Oxidation number of S in H SO 4 =(+)6 Oxidation number of S in SO =(+)4 Oxidation number had decreased S has gained electrons for second mark Second mark stands alone provided oxidation numbers have decreased, even if calculated wrongly Just S has gained electrons without calculating oxidation numbers (b)(ii) Black / (shiny) grey solid Purple / violet / pink vapour / fumes Smell of (bad) eggs Yellow solid Brown liquid Any two Purple solid (b)(iii) Oxidation number of S has reduced more / to (in H S) Oxidation number of S is lower in H S (than in SO ) If ON of S in H S is calculated it must be correct (c) People can choose whether to take extra fluoride Fluoride is not released into the environment Fluoride can be monitored

1 Two white powders, A and B, known to be Group 2 carbonates, are investigated.

1 Two white powders, A and B, known to be Group 2 carbonates, are investigated. (a) (i) The presence of the carbonate ion is usually confirmed using a simple test carried out in two stages at room temperature.