Dynamic Equilibrium Video Lecture - Class 11

in this lesson you will learn about
dynamic equilibrium the conditions
required for dynamic equilibrium to be
reached and examples of systems at
equilibrium
imagine you are digging a hole you got
it
imagine as you are digging that hole
your friend is refilling it if you are
digging the hole faster than your friend
the hole gets larger if your friend is
filling the hole faster than you the
hole gets smaller but if the two of you
are working at the same speed there
would be no change to the size of the
hole the same concept can be applied to
a reversible reaction if the rate of the
forward reaction reactants to products
is the same as the reverse reaction
products to reactants the reaction is
said to be at equilibrium this is called
a dynamic equilibrium because both
processes are occurring simultaneously
even though there is no overall
observable change for a chemical system
such as a reaction or phase change to be
at equilibrium it must meet two
important criteria first it must be a
reversible process second it must be
taking place in a closed system a closed
system is one where there is no exchange
of matter only exchange of energy an
example of a reaction at equilibrium is
the reaction of hydrogen and iodine in a
closed container to produce hydrogen
iodide at the start of the reaction
there is a high concentration of
hydrogen and iodine and the
concentrations decrease as hydrogen
iodide is formed the concentration of
hydrogen iodide increases as the forward
reaction proceeds as hydrogen iodide is
formed the reverse reaction is then able
to occur
over time the concentrations of hydrogen
iodine and hydrogen iodide remain
constant so what is happening here
the reaction of hydrogen and iodine to
produce hydrogen iodide is occurring at
the same rate as the decomposition of
hydrogen iodide to hydrogen and iodine
so there are no observable changes
although both the forward and reverse
reactions are occurring this reaction
has not stopped but rather has reached
dynamic equilibrium what would happen to
this reaction if the lid on top of the
glass jar was opened please pause the
lesson to think about this and resume
when you are done if the lid was removed
the system is no longer at equilibrium
as the reactants and products or matter
would be able to escape the system
liquid bromine equilibrates to form
asius bromine at room temperature
remember that this is not a reaction but
rather a phase change phase changes can
also reach equilibrium under the correct
conditions as liquid bromine evaporates
gaseous bromine condenses since these
two processes are occurring
simultaneously at the same rate there is
no observable macroscopic change but the
system is in fact in dynamic equilibrium
in summary a chemical system is said to
be at equilibrium when the rate of the
forward reaction is the same as the rate
of the reverse reaction there are no
observable changes but both directions
of the reaction are occurring so it is a
dynamic equilibrium