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11. Group 17
A section of Chemistry, 9701
Listing 10 of 617 questions
One major difference between the properties of compounds of the transition elements and those of other compounds is that the compounds of the transition elements are often coloured. Explain in detail why many transition element compounds are coloured. The following graph shows the absorption spectrum of two complexes containing copper. absorbance [Cu(NH3)4(H2O)2]2+ [Cu(H2O)6]2+ wavelength / nm blue green yellow red infra-red State the colours of the following complex ions. [Cu(H2O)6]2+ [Cu(NH3)4(H2O)2]2+ Using the spectra above give two reasons why the colour of the [Cu(NH3)4(H2O)2]2+ ion is deeper (more intense) than that of the [Cu(H2O)6]2+ ion. Predict the absorption spectrum of the complex [Cu(NH3)2(H2O)4]2+, and sketch this spectrum on the above graph. Copper forms a complex with chlorine according to the following equilibrium. Cu2++ 4Cl –2–Write an expression for the equilibrium constant, Kc , for this reaction, stating its units. Kc = units The numerical value of Kc is 4.2 3 105. Calculate the [ 2–] / [Cu2+ ] ratio when [Cl – ] = 0.20 mol dm–3.
9701_w09_qp_41
THEORY
2009
Paper 4, Variant 1
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Questions Discovered
617