Question
(a) (i) To a 1 cm depth of FB 4 in a boiling tube, slowly add a 1 cm depth of dilute nitric acid. Stir gently until the reaction is complete. Use this solution for your tests.
Select reagents to identify which sodium halide is present.
Record details of the reagents used and your observations.
Identify the sodium halide that is present as an impurity in FB 4.
The formula of the impurity is ……
[2]
(ii) Suggest why it is necessary to add the nitric acid to FB 4 before carrying out your tests in
(a)(i).
…… [1]
* 0000800000008 * DFD
8
(b) FB 7 contains a metal cation which is listed in the Qualitative analysis notes.
(i) Place half the sample of FB 7 in a hard‑glass test‑tube. Heat gently at first and then more strongly.
Record your observations.
…… [2]
(ii) Use the 25 cm3 measuring cylinder to measure 20 cm3 of FB 1.
Place the remaining sample of FB 7 in a boiling tube and add portions of FB 1 from the measuring cylinder until all the FB 7 has reacted. Stir until the reaction is complete.
Record your observations.
Keep this solution for use in (b)(iii).
…… [2]
(iii) Carry out the following tests. For each test use a 1 cm depth of the solution from (b)(ii) in a test‑tube.
Record your observations in Table 3.1.
Identify the metal ion present in FB 7.
Table 3.1
test observations
Test 1
Add aqueous sodium hydroxide.
Test 2
Add aqueous ammonia.
Test 3
Add a piece of aluminium foil.
The formula of the metal ion in FB 7 is ……
[4]
* 0000800000009 * DFD
9
(c) FB 8 is an acidified aqueous solution containing a metal cation which is listed in the Qualitative analysis notes.
(i) Carry out the following tests. For each test use a 1 cm depth of FB 8 in a test‑tube.
Record your observations in Table 3.2.
Identify the metal ion present in FB 8.
Table 3.2
test observations
Test 1
Add aqueous sodium hydroxide.
Test 2
Add a 1 cm depth of acidified aqueous potassium manganate(VII).
The formula of the metal ion in FB 8 is ……
[3]
(ii) State the type of reaction between the metal ion in FB 8 and acidified aqueous potassium manganate(VII).
Explain how your observations support your answer.
…… [1]
[Total: 15]
* 0000800000010 * DFD
10
Qualitative analysis notes
1 Reactions of cations cation reaction with
NaOH(aq) NH3(aq) aluminium, Al 3+(aq) white ppt. soluble in excess white ppt. insoluble in excess ammonium, NH4+(aq) no ppt. – ammonia produced on warming barium, Ba2+(aq)
faint white ppt. is observed unless no ppt.
[Ba2+(aq)] is very low calcium, Ca2+(aq) white ppt. unless [Ca2+(aq)] is very no ppt. low chromium(III), Cr3+(aq) grey‑green ppt. soluble in excess grey‑green ppt. insoluble in excess giving dark green solution copper(II), Cu2+(aq) pale blue ppt. insoluble in excess pale blue ppt. soluble in excess giving dark blue solution iron(II), Fe2+(aq) green ppt. turning brown on green ppt. turning brown on contact with air contact with air insoluble in excess insoluble in excess
iron(III), Fe3+(aq) red‑brown ppt. insoluble in excess red‑brown ppt. insoluble in excess magnesium, Mg2+(aq) white ppt. insoluble in excess white ppt. insoluble in excess manganese(II), Mn2+(aq) off‑white ppt. rapidly turning brown off‑white ppt. rapidly turning brown on contact with air on contact with air insoluble in excess insoluble in excess zinc, Zn2+(aq) white ppt. soluble in excess white ppt. soluble in excess
2 Reactions of anions
anion reaction carbonate, CO32– CO2 liberated by dilute acids chloride, Cl –(aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)) bromide, Br –(aq) gives cream / off‑white ppt. with Ag+(aq) (partially soluble in NH3(aq)) iodide, I–(aq) gives pale yellow ppt. with Ag+(aq) (insoluble in NH3(aq)) nitrate, NO3–(aq) NH3 liberated on heating with OH–(aq) and Al foil nitrite, NO2–(aq) NH3 liberated on heating with OH–(aq) and Al foil; decolourises acidified aqueous KMnO4 sulfate, SO42–(aq) gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids);
gives white ppt. with high [Ca2+(aq)]
sulfite, SO32–(aq) gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids); decolourises acidified aqueous KMnO4 thiosulfate, S2O32–(aq) gives off‑white / pale yellow ppt. slowly with H+
* 0000800000011 * DFD
11
3 Tests for gases
gas test and test result ammonia, NH3 turns damp red litmus paper blue carbon dioxide, CO2 gives a white ppt. with limewater hydrogen, H2 ‘pops’ with a lighted splint oxygen, O2 relights a glowing splint
4 Tests for elements
element test and test result iodine, I2 gives blue‑black colour on addition of starch solution
Important values, constants and standards
molar gas constant R = 8.31 J K–1 mol–1
Faraday constant F = 9.65 × 104 C mol–1
Avogadro constant L = 6.02 × 1023 mol–1 electronic charge e = –1.60 × 10–19 C molar volume of gas Vm = 22.4 dm3 mol–1 at s.t.p. (101 kPa and 273 K)
Vm = 24.0 dm3 mol–1 at room conditions ionic product of water Kw = 1.00 × 10–14 mol2 dm–6 (at 298 K (25 °C)) specific heat capacity of water c = 4.18 kJ kg–1 K–1 (4.18 J g–1 K–1)
The Periodic Table of Elements
Group
1 2 13 14 15 16 17 18
1 2
H He hydrogen helium
Key 1.0 4.0
3 4 atomic number 5 6 7 8 9 10
Li Be atomic symbol B C N O F Ne lithium beryllium name boron carbon nitrogen oxygen fluorine neon
6.9 9.0 relative atomic mass 10.8 12.0 14.0 16.0 19.0 20.2
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
DFD
23.0 24.3 3 4 5 6 7 8 9 10 11 12 27.0 28.1 31.0 32.1 35.5 39.9
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
at www.cambridgeinternational.org after the live examination series.
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton
39.1 40.1 45.0 47.9 50.9 52.0 54.9 55.8 58.9 58.7 63.5 65.4 69.7 72.6 74.9 79.0 79.9 83.8
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
12
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
85.5 87.6 88.9 91.2 92.9 95.9 – 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3
55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 lanthanoids
Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon
132.9 137.3 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 – – –
87 88 89–103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 actinoids
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson
– – – – – – – – – – – – – – – – –
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium
138.9 140.1 140.9 144.2 – 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.1 175.0
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium
– 232.0 231.0 238.0 – – – – – – – – – – –
Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download
To avoid the issue of disclosure of answer‑related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge
Mark scheme
3(a)(i) • selects (aqueous) silver nitrate and (aqueous) ammonia * 2
• white ppt *
• soluble in (aqueous) ammonia *
• NaCl *
2 * = 1 mark
3(a)(ii) (The acid) removes / reacts with the hydrogencarbonate ions OR silver ions react with hydrogencarbonate ions 1
3(b)(i) • green (at start) * 2
• turns to a black powder / solid *
• powder very fluid / moves around the test-tube *
• condensation (on walls of test-tube) *
2 * = 1 mark
3(b)(ii) • forms green-blue solution * 2
• effervescence *
• vigorous reaction *
• attempts to test with limewater *
• gas / carbon dioxide gives white precipitate / solid with limewater *
2 * = 1 mark
3(b)(iii) 4
Test 1 (pale) blue precipitate insoluble in excess *
Add NaOH(aq)
Test 2 (pale) blue precipitate *
Add NH3(aq) (precipitate dissolves forming) dark / deep blue solution in excess *
Test 3 effervescence / fizzing*
Add aluminium (gas) pops with a lighted splint *
foil pink-brown solid *
turns colourless / pale blue solution formed *
gets hotter *
Metal ion in FB 7: Cu2+ *
2 * = 1 mark
3(c)(i) 2
green precipitate *
Test 1
insoluble in excess *
Add NaOH(aq)
(precipitate) turns brown (on surface) *
Test 2 purple to colourless / (pale) yellow solution
Add acidified
OR KMnO4 decolourised*
KMnO4
2 * = 1 mark
Metal ion in FB 8: Fe2+ 1
3(c)(ii) Redox reaction 1
AND change to colourless linked to reduction of manganate(VII) ions OR change to yellow colour linked to oxidation of
Fe2+ or production of Fe 3+.