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CIE Nov 2017 v1 Paper 4 Q4
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![(a) Describe and explain how the density and melting point of cobalt compare to those of calcium. PMT density of cobaltexplanationmelting point of cobaltexplanation[3] (b) Transition metals can form complexes. What is meant by the term transition metal complex?[1] (c) (i) Cobalt can form the compounds [Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br. These two compounds are structural isomers. Define the term structural isomer.[1] (ii) Draw a three-dimensional diagram to show the structure of the ion [Co(NH3)5Br]2+. Name its shape. [Co(NH3)5Br]2+ shape[1] (iii) State the type of bonding between the cobalt ion and NH3 groups in the [Co(NH3)5Br]2+ ion.[1]UCLES 2017 9701/41/O/N/17<br />
PMT (iv) State the oxidation number of cobalt in [Co(NH3)5Br]2+ [Co(NH3)5SO4]+ oxidation number of Co =oxidation number of Co =[1] (d) Solutions of the compounds [Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br can be distinguished from each other by simple chemical tests. Assume that any species bonded to the cobalt ion does not react in these tests. Complete the table with two different tests that could be used to positively identify each compound. Give the expected observation with each compound. test observation with [Co(NH3)5Br]SO4(aq) observation with [Co(NH3)5SO4]Br(aq) [2] (e) The two compounds [Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br are different colours. Explain why the colours of the two compounds are different.[2] (f) Some transition metals and their compounds act as catalysts. The catalysis can be classified as heterogeneous or homogeneous. Complete the table by placing one tick () in each row to indicate the type of catalysis in each reaction. heterogeneous homogeneous Fe in the Haber process Fe2+ in the I / S2O8 2 reaction NO2 in the oxidation of SO2 V2O5 in the Contact processUCLES 2017 9701/41/O/N/17 [2] [Total: 14] [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2017_v1_QP_-_Paper_4_CIE_Chemistry_A-level_4-0.jpg)
![9701/41 Question 3(c)(i) Cambridge International AS/A LevelMark Scheme PUBLISHED Answer Q = 0.48060 = 1920 C and use of 96500 / 193000 Moles of Pb = 1920 / 193000 = 9.95103 Mass of Pb = 207.29.95103 = 2.1 g OR Q = 0.48060 = 1920 C and use of 1.61019 atoms Pb = 61021; moles of Pb =61021 / 61023 = 0.01 Mass of Pb = 207.20.01 = 2.1 g / 1.21022 3(c)(ii) 3(d) 2(aq) + 4H+ + 2ePbSO4(s) + 2H2O PbO2(s) + SO4 reagents / PbO2 / H2SO4 and used up / concentration decreases as fuel / hydrogen is being continuously supplied / fuel has not run out Question 4(a) density is higher and melting point is higher (density) due to Ar being larger and smaller atomic radii or (Co) atoms / ions heavier and smaller Answer (melting point) due to stronger attraction to cations as more delocalised electrons (a molecule or ion) formed by a central metal atom / ion surrounded by (one or more) ligands same number and type of atoms and different structural formula 4(b) 4(c)(i)UCLES 2017 Page 5 of 13 PMT October/November 2017 Marks 2 1 1 1 Marks 1 1 1 1 1<br />
Cambridge International AS/A LevelMark Scheme PUBLISHED Answer octahedral AND 3D structure of [Co(NH3)5Br]2+ e.g. PMT October/November 2017 Marks 1 9701/41 Question 4(c)(ii) 4(c)(iii) 4(c)(iv) 4(d) 4(e) 4(f) co-ordinate / dative covalent +3 for both / AgNO3 cream(yellow) ppt. (of AgBr) and no reaction / white ppt. for other isomer (HNO3) Ag+ Ba(OH)2 / Ba2+(aq) / BaCl 2 / Ba(NO3)2 white ppt. (of BaSO4) and no reaction for other isomer (d-d) energy gap / E is different absorb different wavelength / frequency (of light) heterogeneous homogeneous Fe in the Haber process Fe2+ in the I reaction / S2O8 2 NO2 in the oxidation of SO2 V2O5 in the Contact processUCLES 2017 Page 6 of 13 (cid:57) (cid:57) (cid:57) (cid:57) 1 1 1 1 1 1 2<br />](https://learnah.org/wp-content/uploads/2018/08/November_2017_v1_MS_-_Paper_4_CIE_Chemistry_A-level_4-0.jpg)
