Question

which of the following describes a reversible reaction? a combines with b and becomes ab, but when ab is heated, it becomes a and b again. c and d combine to form cd. ef breaks down into e and f. ab and cd react to become ac and bd.

Explanation:

A reversible reaction can proceed in both the forward and reverse directions. In the first option, A and B combine to form AB (forward reaction), and AB can break - down back into A and B (reverse reaction) upon heating. The other options only show one - way reactions: combination or decomposition.

Answer:

A. A combines with B and becomes AB, but when AB is heated, it becomes A and B again.