Which formula equation shows a reversible reaction?
a. 2na+f2–> 2naf
b. caco3–> cao+co2
c. nh4ci(s)—–nh3(
g.+hci(
g. 2h2o2(aq)–pt—> 2h2o(i)+o2(g)

Explanation:

A reversible reaction is indicated by using a double arrow ⇄

The upper arrow (→), from left to right,  indicates the direct or forward reaction, which goes from left to right.

In the direct reaction, the reactants are the substances shown on the left side of the equation, and the products are the substances shown on the right side.

The lower arrow (←), from right to left, indicates the reverse reaction, which goes from right to left.

In the reverse reaction, the reactants are the substances shown of the right side and the products are the substances shown of the left side.

Summarizing:

In the moment that the rates of both forward and reverse reactions are equal it is said that the equilibrium has been reached.