Everything about Dynamic Equilibrium totally explained
A
dynamic equilibrium occurs when two opposing
processes proceed at the same rate. A
reversible chemical reaction will be at dynamic equilibrium when the rate of forward reaction is equal to the rate of the reverse reaction. Whilst at dynamic equilibrium there's no change in the concentration of either the forward or reverse reactions. The word "
dynamic" indicates that at equilibrium both the forward and reverse chemical reactions still occur rather than the reaction halting once equilibrium is reached.
An example of dynamic equilibrium, for a closed and partially filled
water bottle water will
evaporate from the surface of the water and the air in the bottle will begin to become
saturated with
water vapor. Eventually, the air will be completely saturated with water vapor, this water will then condense as its molecules collide with the surface of the water. When the rate of evaporation is equal to the rate of condensation the system is at dynamic equilibrium.
The concept of dynamic equilibrium isn't limited to simple changes of state such as that described above. It is often applied to the analysis of chemical
reaction kinetics, to obtain useful
information about the ratios of reactants and products which will form at equilibrium. It should be noted that at equilibrium the concentrations of the reactants and the concentrations of the products are constant.
The term also has applications across a wide range of disciplines. While it may be applied to less physical systems in these fields, it still relates to a stable situation maintained by balancing processes. For example: in
economics it may be used to refer to the constant flux of
capital in otherwise stable markets; in
ecology, an unchanging
population of
organisms results from the balancing of
birth rate against
death rate.
This term can also be used to refer to a
steady state (for example, a state which isn't a true equilibrium, but doesn't change with time). This can only happen if the system is in contact with an environment which isn't in equilibrium. A prime example is that of most stars - nuclear fusion provides an outward pressure to counteract the pressure of gravity, but neither the fusion continually produces energy, and the environment external to the star is certainly not in equilibrium, either.
Equilibrium Constant K
If a system is in dynamic equilibrium, a constant ratio of concentrations for that equilibrium can be described.
In general, for the reaction aA + bB
↔ cC + dD, K is given by one of the following
equilibrium constant expressions:
(i)
where
P indicates
partial pressure and square brackets indicate
concentration in molarity; that is, number of
moles per
litre of solution.
When both reactants and products are in the
gaseous phase, the Equilibrium Constant is referred to as K
P, and equation (i) is used; when reactants and products are all in solution, the Equilibrium Constant is referred to as K
C, and equation (ii) is used.
The two can be related by the
ideal gas law,
,
where
» is the absolute pressure of the gas,
is the volume of the gas,
» is the number of moles of gas,
is the
universal gas constant,
» is the
absolute temperature.
Further Information
Get more info on 'Dynamic Equilibrium'.
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