6.1. Redox processes: electron transfer and changes in oxidation number (oxidation state)
A subsection of Chemistry, 9701, through 6. Electrochemistry
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Manganese, chromium and ruthenium are all transition elements. Explain what is meant by a transition element. MnO4 –and Cr2O7 2–act as oxidising agents in acidic solution. Both these oxidising agents will oxidise a solution of Sn2+ to give a solution of Sn4+. Solutions containing Sn2+ and solutions containing Sn4+ are colourless. Describe the colour change seen when an excess of Sn2+is added separately to ● dilute acidified MnO4 –from to ● dilute acidified Cr2O7 2–. from to  Write an equation for the reaction between Sn2+and acidified Cr2O7 2–. Ruthenium, Ru, forms complex ions. In one such complex ion, X, the ruthenium ion has a co‑ordination number of six. Each complex ion X contains one Ru2+ ion, one Cl – ion, one SO2 molecule and the remaining ligands are NH3 molecules. The SO2 molecule acts as a monodentate ligand and is attached to the Ru2+ ion via the sulfur atom. X exists in two isomeric forms. State what is meant by a co-ordination number of six. State the formula of X. Include its charge. Draw the two isomeric forms of X in the boxes below. Your diagrams should show ● ● the three-dimensional shapes of the two isomers ● ● how each ligand is attached to the central ruthenium ion. Ru Ru  Suggest the type of isomerism shown by X. Explain the origin of colour in a transition element complex such as X. 
9701_w19_qp_41
THEORY
2019
Paper 4, Variant 1
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