2.3.1 Dynamic Equilibrium

Reversible reactions the reaction arrow ( ⟶ ) is replaced with the equilibrium sign ( ⇌ )

$$Br_2(g) ⇌ Br_2(l)$$

For a reversible reaction in a closed system, a dynamic equilibrium can occur. In which the rates of the forward and reverse processes are the same.

The moment the bromine evaporates, the increased collisions make some gas lose energy and turn back to liquid.

The consequence is no changes, as the forward and backward reactions cancel each other out. On the macroscopic level the changes stop but not at the microscopic.

Heterogeneous equilibriums

The former image represents a heterogeneous equilibrium, as both participating species are in different phases. Another example of this type of equilibrium is with solid substance in excess and a solution .

Mixing excessive $NaCl(s)$ with water will form constuients of the molecule as it dissolves, but some may form back to sodium chloride through precipitation.

NaCl(s) ⇌^ {dissolution}_{precipitation} Na^

unsaturated solution contains less solute than possible. The highest possible concentration of the solute in a solution under given conditions is known as the solubility of that solute.

Chemical Equilibirums

• Reversible chemical reactions at the same time.

typical example

The presence of the equilibirum sign indicates that two processes take place the same time at equal magnitudes and is constantly happening.

1. Synthesis of Ammonia ( forward reaction )

2. Decomposition of Ammonia ( backwards reaction )

Chemical Equilibirum can be achieved from any initial state of the system. In the example, strated with the concentrations of $1.00 \text { mol dm}^{-3}$ of nitrogen $3.00 \text { mol dm}^{-3}$ of hydrogen and no ammonia.

The equilibrium concentrations were then $0.50,1.50, 1.00 \text{ mol dm}^{-3}$ respectively. The same equilibrium concentrations of all three species will be produced if I started with $2.00 \text{ mol dm}^{-3}$ of ammonia instead.

the ammonia instead of being formed will be decomposed instead