Question

Question: Iron oxides are red when the average oxidation state of iron is high and black when it is low. To impart each of these colors to a pot made from clay that contains iron oxides, would you use an air-rich or a smoky atmosphere in the kiln? Explain.

Short answer

The red colour is due to the use of air rich atmosphere in the Klin which result in the formation of iron oxide with a higher oxidation state and the black colour appear due to the use of smoky atmosphere in the same with a lower oxidation state.

Step-by-step solution

Step 1:

The colour of ${\mathrm{Fe}}_2{\mathrm{O}}_3$is red colour when Fe is with higher oxidation state.

The colour of ${\mathrm{Fe}}_3{\mathrm{O}}_4$is black colour when the Fe atom is with lower oxidation state.

Step 2:

The red colour is due to the use of air rich atmosphere in the Klin which result in the formation of iron oxide with a higher oxidation state and the black colour appear due to the use of smoky atmosphere in the same with a lower oxidation state.