The newest 20 of 83 written questions. Open one to see it on the real paper.
Explain why a transition element, such as cobalt, has variable oxidation states in its compounds.
See it on the paper →Explain what is meant by bidentate ligand.
See it on the paper →State the formula and charge of this complex.
See it on the paper →State two reasons that explain why chromium compounds can behave as catalysts. lleccete eese
See it on the paper →Explain why transition elements behave as catalysts.
See it on the paper →The 3d orbitals in an isolated Cu 2+ ion are degenerate. Complete the diagram to show the relative energies of the 3d orbitals in an isolated Cu 2+ ion and in Cu 2+ in a tetrahedral complex. energy isolated Cu 2+ ion Cu 2+ in a tetrahedral complex
See it on the paper →Explain why transition elements behave as catalysts.
See it on the paper →CN – is a monodentate ligand. Table 5.2 shows information about two complex ions that contain only CN – ions as ligands. Complete Table 5.2. Table 5.2 metal ion coordination number Ag + 2 formula of complex ion Fe 2+ charge of complex ion 4–
See it on the paper →A few drops of NH 3 (aq) are added to CuSO 4 (aq). Describe any observations made.
See it on the paper →Write an equation for the reaction taking place. (ii)
See it on the paper →Iron is a transition element. Explain why iron forms stable compounds in both the +2 and the +3 oxidation states.
See it on the paper →Explain why transition elements form complex ions.
See it on the paper →Deduce the formula of complex ion G. Include its overall charge. formula of G (i)
See it on the paper →Write an ionic equation for this reaction, using the formulae of the complex ions.
See it on the paper →Explain why transition elements form complex ions.
See it on the paper →Deduce the formula of complex ion G. Include its overall charge. formula of G (i)
See it on the paper →Write an ionic equation for this reaction, using the formulae of the complex ions.
See it on the paper →Explain why transition elements can form complex ions.
See it on the paper →Tollens’ reagent can be used to distinguish between aldehydes and ketones. Tollens’ reagent contains [Ag(NH 3 ) 2 ]OH, which can be prepared in a two-step process. step 1 Aqueous NaOH is added dropwise to aqueous AgNO 3 to form Ag 2 O as a brown precipitate. step 2 Aqueous NH 3 is added dropwise to Ag 2 O to form a col...
See it on the paper →The anhydrous iron( III ) compound K 3 [Fe(C 2 O 4 ) 3 ] decomposes on heating to form a mixture of K 2 [Fe(C 2 O 4 ) 2 ], K 2 C 2 O 4 and CO 2 . Complete the equation for the decomposition of K 3 [Fe(C 2 O 4 ) 3 ]. K [Fe(C O ) ] K [Fe(C O ) ] + K C O + CO
See it on the paper →Comprehensive responses • Most candidates identified that chromium compounds have more than one oxidation state. Limited responses • Some candidates did not explain that d-orbitals needed to be vacant.
— Examiner report, February/March 2026, 9701/42 Q1(a)(iv) (Cambridge)
Candidates found this question difficult. Many suggested the coordination number was six instead of eight.
— Examiner report, October/November 2023, 9701/41 Q5(b)(i) (Cambridge)
This discriminated well. The key information in the question is that the named complex is octahedral. Each EDTA4– ligand must donate six lone pairs for this to be true.
— Examiner report, October/November 2023, 9701/42 Q4(c) (Cambridge)
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