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The problem we have a buffer same buffer we worked a little while ago that we found the original
PH of this buffer was 9.15 but now are gonna add 125 ml of 0.1 molar nitric acid
not because we're mixing two solutions together
the molar these of each solution will change we have to use
power dilution formula and 1B1 equals into the two
for every chemical that's involved in the reaction every time you mix together two solutions
so for example this case
we have
an H3 hand and each four plus in our regional buffer
and two that buffer we're adding nitric acid
when you identify every chemical
we have a strong acid added two a solution that a week base
with its kanji get acid
the strong acid nitric acid
will react with a base
in the donate a proton because its strong as long as one chemical as strong an reaction
this will be a single a row a complete reaction
and we're going to make an H4 plus
and nitrate
so for every chemical this part of this ice chart
we need to do our dilution shortcut and 1B1 = two the two we do this for the nitric acid
them one is a starting molar dei which was 0.1
the one is the volume of that solution use which was 125 ml
and 2 to 2 lead in molar these wartime this all for and the two is that old bowl volume
when two solutions are makes together in this case
one leader co 1000 ml of the buffer was added 225 ml of the acid which makes are total volume
1125
so the nitric acid concentration decreased from 0.1
down 2.0111
and the like carry out a lot of gas while places when we do this so we don't make a rounding error in our ice chart
were also in and do this for
ammonia and
ammonium
so here I completed and one deal and exam to the two for the ammonia and the ammonium
they both were 1000 ml initially notice the total volume
for a solution has to be the same for every chemical in that solution 1125 in this case
and so we have the power diluted molar these
this is just the start of our ice chart because now we have
the molar these now we can write
power ice chart
so the acid donates a proton
to the base
and we're going to make more ammonium
and nitrate
using RM one the one and two the two values we get the starting molar dei of the nitric acid 0.0111 the ammonia was 0.3556
and the Monet and was 0.4444
the only one that to zero as the nitrate because we don't have any nitrate before the chemical reaction started
with this ice chart we know are gonna go to the right because we have a zero for the nitrate and we know the reaction is going to be complete
so in this case the nitric acid is are limiting react and and all of eight gets used up
so we decrease the amount of ammonia
and we increase the amount of
ammonium
so that this point
you have to identify it what you have left after this ice chart
zero of the strong acid because all the strong acid reacted away
we still have some weak base we have Selma Monet and which is the conjugate acid of that week base
and we have nitrate the nitrate is the kanji get of the strong acid and the kanji get so strong acids do not react with water
so after this reaction
we still have a buffer
and we recognize you have a buffer you can use the Henderson also Bach formula
to calculate the PH
we had the PK A
rad the negative log of the ammonium cat ions Kay value that was 9.25
and then the ratio base over acid
the base is 0.3445 and the acid was 0.4555
so the PH Works out to be 9.13
notice the PH before we added anything
was 9.15
very small change because we have a buffer
and notice that the change was
decreasing
when we added this strong acid it's going to make the solution a little bit more acidic
because look at a rice chart were decreasing the amount of base and we're increasing the amount
of acid by this chemical reaction if we had added a strong base the PH with the increased by a little bit
in this case the PH dropped
but it doesn't drop very much because that's
what a buffer dots