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CIE Jun 2013 v2 Paper 4 Q4
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![(a) (i) Suggest why transition elements show variable oxidation states in their compounds whereas s-block elements like calcium do not. Examiners For Use(ii) Calculate the oxidation number of the metal in each of the following ions.VO2 CrF6 MnO4 2 2[4] (b) Explain why transition element complexes are often coloured whereas compounds of s-block elements such as calcium and sodium are not.[4] (c) SO2 and MnO4react together in acidic solution. (i) Use the Data Booklet to construct a balanced equation for this reaction.(ii) Describe the colour change you would see when SO2(aq) is added to a sample of acidi ed KMnO4 until the SO2 is in excess. fromto[3] (d) Describe the observations you would make when NH3(aq) is added gradually to a solution containing Cu2+ ions, until the NH3 is in an excess.[3] [Total: 14]UCLES 2013 9701/42/M/J/13<br />](https://learnah.org/wp-content/uploads/2018/08/June_2013_v2_QP_-_Paper_4_CIE_Chemistry_A-level_4.jpg)
![Page 6 Mark Scheme Syllabus Paper GCE A LEVELMay/June 2013 9701 42 PMT OH or -ONa or -O NOT -NaO (d) (i) or NH NH Br Br Br (ii) NaNO2 + HCl or H2SO4 or H or HNO2 T10 (e) (i) amide (ii) M r = 108+11+14+16 = 149 %N = (14 x 100)/149 = 9.4% (iii) NHCOC [1] + [1] [1] [1] [4 max 3] [1] [1] [1] [3] [Total: 11] 4. (a) (i) Many electrons of similar energy in a valence-shell orbital or successive ionisation energies rise steadily (no big jumps) or ability to form bonds with ligands can stabilise very low or very high oxidation states or 4s + 3d orbitals/shells/energy levels have similar / same energies (ii) VO2 : +5 CrF6 : +4 2 MnO4 : +6 2 [1] [31] [4]Cambridge International Examinations 2013<br />
PMT Page 7 Mark Scheme Syllabus Paper GCE A LEVELMay/June 2013 9701 42 (b)(colour due to) absorption of light/photons/frequencies/wavelengths or colour seen is complement of colour absorbed.d-orbitals/d-subshell split (by ligand field)(when photon is absorbed), electron is promoted or moves (from lower) to higher (d)orbitalenergy difference/gap or E or splitting corresponds to photon/frequency/wavelength in visible regionin s-block elements the energy gap is too large (to be able to absorb visible light) [any four 41] (c) (i) 2MnO4 + 2H2O + 5SO22Mn + 5SO4 + 4H 2+ 2 (ii) solution will go from purple to colourless (d) (pale) blue solution gives a (pale) blue ppt. which re-dissolves, or forms a solution, which is dark/deep blue or purple [4] [1] [1] [1] [3] [1] [1] [1] [3] [Total: 14]Cambridge International Examinations 2013<br />](https://learnah.org/wp-content/uploads/2018/08/June_2013_v2_MS_-_Paper_4_CIE_Chemistry_A-level_4-0.jpg)
