What does the arrow in a chemical equation indicate about the relationship between reactants and products?

• A. Reactants react to form products.
• B. Products always convert back to reactants.
• C. Reactants and products exist independently with no relation.
• D. The reaction occurs instantaneously.

Answer: (A)

The arrow in a chemical equation shows the direction of the chemical change from starting materials to what is formed. It tells you that the substances on the left (reactants) are transformed into the substances on the right (products). In most simple equations this forward direction is what the arrow represents. If a reaction can go both ways, a double-headed arrow is used to show that products can convert back into reactants. So the idea is about conversion: reactants are changed into products, not that they exist independently, always revert, or happen instantly.