What symbol is used in chemical equations to indicate that a reaction is reversible?

In chemical equations, a double arrow is used to indicate that a reaction is reversible. This signifies that the reactants can form products, and those products can also revert back to the original reactants. Reversible reactions are often dynamic in nature, and this double arrow reflects the idea that the reaction can proceed in both directions under certain conditions.

When examining the other symbols: a single arrow typically denotes a reaction that goes only one way, leading to the formation of products without reverse; a plus sign is used to separate different reactants or products in a reaction; and an equals sign is not used in standard chemical notation for reactions as it suggests a static equivalence rather than the dynamic process of chemical transformation. Thus, the double arrow is the correct choice for representing reversible reactions.