A menudo se recomienda que deje que el motor de su automóvil funcione al ralentí para calentarse antes de conducir, especialmente en los fríos días de invierno. Si bien el beneficio del ralentí prolongado es dudoso, es cierto que un motor caliente es más eficiente en el consumo de combustible que uno frío. Explique la razón de esto. Respuesta

See explanation

Explanation:

From the analysis we have in the question, we must look towards a first row transition metal ion having a d^6 configuration because it yields a paramagnetic complex having four unpaired electrons and a diamagnetic complex having no unpaired electrons.

We have two possible candidates in mind, Fe^2+ and Co^3+. However, Fe^2+  does not form as many coloured complexes as stated in the question so we have to eliminate that option.

We are now left with only Co^3+. Various ligands are going to cause these various colours of Co^3+ to appear in solution.

Hence, we can deduce from all these that the nature of ligands determines the colour of the complex . Don't forget that the colour of a complex arises from crystal field splitting.