A-LevelChemistryAtomic structure9701/41 · Oct/Nov 2018 · Q319 Marks
The reaction scheme shows some reactions of [Cu(H2O)6]²⁺. [Figure showing reaction scheme: [Cu(H2O)6]²⁺ reacts with NaOH(aq) to form precipitate A (reaction 1), with excess NH3(aq) to form solution B (reaction 2), and with CuCO3(s) (reaction 3) which then reacts with CH3CO2H(aq) to form solution C (reaction 4).] Platin, Pt(NH3)2Cl2, is a neutral complex of platinum(II).
- (a)Complete the table to show the total number of unpaired electrons in the 3d and 4s orbitals of each isolated gaseous atom. number of unpaired electrons 3d | 4s ----|---- Cr | | Mn | | Fe | | [2][2]
- (b)Solid potassium manganate(VII), KMnO4, decomposes on heating to form manganese(IV) oxide, potassium manganate(VI) and a colourless gas. Construct an equation for this reaction. [2][2]
- (c)Explain the origin of colour in transition element complexes. [3][3]
- (d)(i)Write the formulae of precipitate A, ..................................................................................................................................... complex ion B, ................................................................................................................................... compound C. ................................................................................................................................... [3][3]
- (d)(ii)Identify a suitable reagent for reaction 3. [1][1]
- (d)(iii)Write an equation for reaction 4. [1][1]
- (d)(iv)Describe two visual observations that would be made during reaction 4. [1][1]
- (e)Explain why Pt(NH3)2Cl2 has no charge. [1][1]
- (f)(i)Pt(NH3)2Cl2, displays cis-trans isomerism. Draw the structure of trans-platin. State its shape and the Cl–Pt–Cl bond angle. shape ................................................................. Cl–Pt–Cl bond angle ........................................... [2][2]
- (f)(ii)Cis-platin is an effective anti-cancer drug. Describe the action of cis-platin in this role. [2][2]
- (g)The use of cis-platin can cause side effects so nedaplatin has been developed. Nedaplatin can be synthesised from cis-platin, Pt(NH3)2Cl2, by replacing the two chloride ion ligands with a single bidentate ligand as shown. Suggest the structure for nedaplatin. Pt(NH3)2Cl2 + [O⁻-C(=O)C(=O)-O⁻] → nedaplatin [1][1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.
- [1] for each column
- Table entry for Cr: 3d = 5, 4s = 1
- Table entry for Mn: 3d = 5, 4s = 0
- Table entry for Fe: 3d = 4, 4s = 0
- [1] formulae of K2MnO4 and O2
- [1] rest of the equation
- [1] M1 d orbitals split into two levels / lower and upper orbitals
- [1] M2 visible light is absorbed and the complementary colour observed
- [1] M3 electron(s) promoted / excited
- [1] precipitate A [Cu(H2O)4(OH)2] OR Cu(OH)2
- [1] solution B [Cu(NH3)4(H2O)2]²⁺
- [1] solution C Cu(CH3CO2)2
- [1] Na2CO3 or CO3²⁻
- [1] CuCO3 + 2CH3CO2H → Cu(CH3CO2)2 + CO2 + H2O
- [1] any two for one mark
- fizzing / bubbles / effervescence
- solid disappears
- green / blue solution (formed)
- [1] sum of the charges of the (four) ligands equals the oxidation number / charge of Pt OR a calculation Pt +2, NH3 neutral / no charge, both Cl¯'s −1 (so no overall charge)
- [1] [Diagram of trans-platin]
- [1] square planar and 180°
- [1] M1 this can bond / bind with DNA
- [1] M2 which prevents replication of the DNA / strand OR prevents cell division
- [1] [Diagram of nedaplatin]
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