Reversible Reactions
Reversible Reactions
Some reactions can take place in two directions. In one direction the reactants combine to form the products. This is called the \(\color{orange}{\text{forward reaction}}\). In the other direction, the products react to form the reactants again. This is called the \(\color{purple}{\text{reverse reaction}}\). A special double-headed arrow ( \(\leftrightharpoons\)) is used to show this type of \(\color{blue}{\text{reversible reaction}}\):
\(\text{XY} + \text{Z}\) \(\leftrightharpoons\) \(\text{X} + \text{YZ}\)
Definition: A reversible reaction
A reversible reaction is a chemical reaction that can proceed in both the forward and reverse directions. In other words, the reactants and products of the reaction may reverse roles.
Fact:
Remember that \(\to\) implies that A goes to B and cannot become A again. \(\rightleftharpoons\) implies that the reaction is reversible. A can go to B and B can go to A.
So, in the following reversible reaction:
\[\overset{{\color{orange}{\textbf{forward}\longrightarrow}}}{\text{H}_{2}\text{(g)} + \text{I}_{2}\text{(g)}} {\color{blue}{\leftrightharpoons}} \underset{\color{purple}{\longleftarrow\textbf{reverse}}}{2\text{HI(g)}}\]
\(\color{orange}{{\text{H}}_{2}{\text{(g)}} + {\text{I}}_{2}{\text{(g)}} \to {\text{2HI(g)}}}\) is the \(\color{orange}{\text{forward}}\) reaction.
The forward reaction is always taken from the given equation and written: left to right.
\(\color{purple}{{\text{2HI(g)}} \to {\text{H}}_{2}{\text{(g)}} + {\text{I}}_{2}{\text{(g)}}}\) is the \(\color{purple}{\text{reverse}}\) reaction.
The reverse reaction is always taken from the given equation and written: right to left.
This lesson is part of:
Chemical Equilibrium