m-chlorobenzaldehyde on treatment with 50% KOH solution yields :

Products A and B formed in the following set of reactions are

The orange colour of $$\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$$ and purple colour of $$\mathrm{KMnO}_4$$ is due to

The coordination geometry around the manganese in decacarbonyldimanganese $$(0)$$ is