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When excess ammonia is added to an aqueous solution of CuSO4, a product X is formed (CuSO4(aq) + 4NH3 -> X). Which of the following is the formula of the complex ion X?

1. [Cu(NH3)4]2+
2. paramagnetic
3. coloured
4. of a magnetic moment of 1.73 BM

Correct answer: [Cu(NH3)4]2+

Solution

Cu2+ reacts with four NH3 ligands to form the deep blue tetraamminecopper(II) ion, [Cu(NH3)4]2+. The other options describe its properties, but only the formula answers 'X is'.

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