okay let's try a couple problems regarding gaseous equilibria
number one a change in volume does not alter which of these equilibria so we
have four options here and altering the volume of the vessel would have an
impact on each of these equilibria except once so figure out which one it
will not have an impact on and then number two consider the following
equilibrium where we have two so2 plus o2 yields two so3 and we have some
thermo chemical data as well the Delta H is negative 198 kilojoules per mole
which condition favors the forward reaction in other words which of these
things will push the reaction or push the equilibrium in the forward direction
so if you need to review some information about equilibria and in
particularly chatelier's principle check out my tutorial on that topic now and
when you're ready give it a try
so looking at the first one a change in
volume we're trying to see how a change in volume would alter with these
equilibria notice that all of these equilibria have gaseous substances
they're all gases and so we know that if we change the volume it is going to have
an impact and which side is favored or which way the equilibrium is going to be
shifted because if we increase the volume the pressure will drop and the
equilibrium will move towards the side with more gaseous particles so as to
reclaim some of the lost pressure by contrast if we reduce the volume that
will increase the pressure and therefore the equilibrium will shift to the side
with fewer gaseous particles so as to relieve some of that additional pressure
so the only way for a change in volume to have no effect on the equilibrium is
if the number of moles of gas particles on each side is the same so if we look
at this that's got to be option we've got two moles of gas on the left
and we've got two moles of gas on the right so there's no way for a change in
volume to have any impact here with the other options for B we've got one on the
left two on the right for C we've got four on the left two on the right and
four D we've got one on the left two on the right so a change in volume would
have an impact on each of those now looking at number two what do we have
here well we have some thermo chemical data and we see that this is an
exothermic reaction which means it is producing Heat so we can consider heat
to be a product here so we can imagine the word Heat on the right side so we're
producing Heat in the forward direction so what this means is that if we lower
the temperature meaning we're removing heat from the products side that is
going to shift this equilibrium to the right likewise if we increase the
pressure that is also going to shift this to the right because we have three
moles of gas particles on the left and two moles of gas particles on the right
so these are the two conditions that would result in equilibrium being
shifted to the right that is lowering temperature and raising pressure and so
that is going to be option B because that correlates with these conditions
that we just listed so that's a little bit of practice regarding gaseous equilibria.