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What is the oxidation number of chromium in the complex ion [Cr(NH3)4Cl2]+ ?

1. 0
2. +1
3. +2
4. +3

Correct answer: +3

Solution

In the complex ion [Cr(NH3)4Cl2]+, ammonia (NH3) is a neutral ligand contributing no charge, while each chloride (Cl) has a charge of -1. To balance the overall charge of +1 for the complex, chromium must have an oxidation state of +3.

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