Concept:Corrosion of metals requires two essential environmental substances: moisture and oxygen.
Explanation:For rusting to occur, metallic iron must be in contact with both water and oxygen.
Water acts as an electrolyte, allowing ions to move during the electrochemical reaction.
Oxygen is needed to accept electrons and form the oxide layer that eventually becomes rust.
If only dry oxygen is present, corrosion does not take place because no electrolyte exists.
If only pure water without dissolved oxygen is present, no oxidation reaction can proceed.
Carbon(IV) oxide is not a necessary condition for ordinary rusting.
The chemical process can be summarised as iron reacting with
O2 in the presence of
H2O.
Thus, the correct pair of conditions is water and oxygen.
Answer:B. Water and Oxygen