How many oxygen (O) atoms are involved in this chemical reaction?

2Fe (OH) 3 - Fe2O3 + 3H20

6 oxygen atoms

Explanation:

From the equation,

2Fe (OH) ₃ → Fe₂O₃ + 3H₂O

From the reactant (left hand side) we have 2 moles of Fe (OH) ₃ having (2 * 3 = 6) atoms of oxygen and decomposed to give Fe₂O₃ which contains 3 atoms of oxygen and 3 moles of water that also contains 3 atoms of oxygen.

Since the number of oxygen participating in the reaction is independent on the product (not a reversible reaction) then the total number of oxygen atoms participating in the reaction is 6