00:01
Question we are going to be finding the ph of the solution at various points when we add malonic acid which i've indicated as h mal plus sodium hydroxide which is a strong base so monic acid is a weak acid sodium hydroxide strong base weak acid strong base so that means that the salt that we form is going to be a basic salt and at the equivalence point that's all we'll have, and that basic salt is going to be a weak base.
00:33
So we are also going to need to have our kb value.
00:36
So to find that, we take, excuse me, kw, 1 ee negative 14, divided by the ka, which is 1 .42 ee negative 3, and kb will equal 7 .04 times 10 to the negative 12.
00:56
We should also find our our equivalence point and our half equivalence point.
01:03
So the equivalence point we will find when you take molarity times volume and set it equal to molarity times volume.
01:09
So 40 times 0 .2 divided by 0 .1 is going to be 80.
01:20
And so the half equivalence point is going to be at 40 milliliters.
01:29
So most of what we are doing, let me just double check, 40 mils of 0 .2 with 0 .1.
01:36
Okay, so most of what we are doing here is in the buffer zone, and we have just one equation that we will use for that.
01:45
Okay, so in fact, at the points that we have, we'll never even reach the equivalence point.
01:55
That's kind of odd.
01:57
Hope that you have the right information here in your prompt.
02:04
Okay, well, is what it is.
02:07
So we first need to calculate our ph of the malonic acid when it's just that malonic acid so at zero milliliters of base added our h plus constant whoops our ka for weak acid ka equals our h plus concentration squared over the concentration of that weak acid now we're trying to find that h plus so one point four two times ten to the the negative third equals h plus concentration squared over 0 .20.
02:47
So 1 .42 ee negative 3 times 0 .2.
02:52
And then we want to take the square root of that.
02:54
And your h plus concentration will equal 0 .0169 molar.
03:06
And then to find the ph, we take the negative log of that value.
03:10
And that will give you 1 .77.
03:16
Okay, so now the rest of these are all in the buffer zone.
03:20
So the only equation we'll use is this one right here.
03:25
So h plus equals ka times our acid info over our base info.
03:35
So the ka is 1 .42 times 10 to the negative third.
03:40
And to start out with, width, we have, we'll figure out our millimoles.
03:46
So we take 40 times 0 .2.
03:48
So that's eight.
03:49
We have eight millimoles of this malonic acid in there, and there's no base...