00:01
Glycine hydrochloride is the fully protonated form of glycine.
00:08
Glycine with an extra hydrogen making it positively charged is going to react with the added hydroxide in the form of sodium hydroxide in order to produce glycine.
00:21
The zwitterion of glycine that's neutral plus water.
00:27
This in our case is going to be the base and this will be the acid.
00:31
Every mole of hydroxide we add makes a mole of the basic form of glycine, the deprotonated form, the singly deprotonated form.
00:42
This still has another hydrogen it can donate associated with pka2, but because we're working with the fully protonated form and the singly deprotonated form, we're working with pka1 for this buffer.
00:56
Then we can use the henderson -hasselbalch equation where ph equals pka plus the log of the moles of the base divided by the moles of the acid.
01:10
Oftentimes people will use molarities, a ratio of molarities here, rather than a ratio of moles, but it's equivalent to use a ratio of moles and often makes the calculation easier.
01:22
So that's what i'll use.
01:24
We want to achieve a ph of 2 .72.
01:28
We'll set that equal to the pka of 2 .350 and then add to that the log of the moles of the base that we're going to form.
01:40
Again, every mole of hydroxide we add will make a mole of the base, so that's going to be x.
01:46
That'll correspond to the moles of sodium hydroxide we need to add.
01:50
We'll then divide that by the moles of the acid still left in solution.
01:55
We started with 0 .120 liters of glycine hydrochloride at a concentration of 0 .018 moles per liter...