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The problem we have a weak acid but the difference what this week acid from the ones you
RT scene is it has two protons that can be donated to water
this is an example of a poly product or are specifically in this case a byproduct acid
died protocol acids or type Roenick acids donate one proton at a time to water
so here's the first ice chart that we need
the weak acid donates a proton water we get an equilibrium that makes hide rhodium and the con to get base of the original acid
we know the reaction is gonna go to the right
so we can solve for acts using that first
K a value eight times 10 to the negative fifth
small value of K and
the reaction is going to end up with mostly all react and so we can try the approximation method first
in when you do the approximation
acts is 7.48 times 10 to the negative third
which is
1.1% so the approximation is valid
but this isn't the only reaction that takes place
now we have the second donation of a proton
the chemical it was the kanji get base in the first equilibrium is now of the acid in the second one donating a proton to water
HC 6H6O6 was not put into the original
ice chart that when started at the concentration of zero
but the first reaction made acts
so our value for acts is our starting point in our second ice chart
H2 liquid we can still cross out and also notice hide rhodium was also made from the first ice chart
and that was also acts
so the starting number is also 7.48 times 10 to the negative third
the conjugate base of this acid the Anaheim with a -2 charge
was not made the first reaction so that one is still zero
but because it zero we know the reaction has to go to the right
and just like always we use the KA the swans the second KA
1.6 times tend to the -12th
notice the second K is even smaller than the first one
the K is get smaller as
the acid keeps donating its protons KA 1 is always larger than K2K2 would always be greater than K3 and saw
now because this K isn't even smaller
we know that this approximation that that should be valid here we can make like this acts in the numerator that's being added
we can also would like this acts in the denominate are the tubing subtracting
and if the assumption that that is valid that makes is probably the major canal 7.48 times than the -3
cancels and we're left with acts is just the second KA 1 0.6 times tend to the negative plus
if you do the approximation you're gonna find it that's definitely less than
5% so the Sump shun that it is valid here are
and so now the ultimate question was once the PH and once the POH
so we need the concentration of hydro nahum
we take this answer for acts and plug it into this ice chart
the PH is
7.48 times the -3 if we have acts do it we know that that's not gonna change
our value the PH Works out to be 2.13
and the POH subtract up from 14
11.87