00:01
When we are titrating a strong acid with a strong base, to calculate the ph, we simply need to determine what is in excess.
00:09
If we're starting with the strong acid and we're titrating it by adding the strong base, with the two concentrations being equal, the two volumes will be equal.
00:22
So if we're titrating 40 milliliters of hcl, we will need 40 milliliters of sodium hydroxide.
00:30
So that means anything less than 40 milliliters of sodium hydroxide will have excess hcl in solution and the solution will still be acidic.
00:42
So at 23 milliliters we have excess hcl.
00:49
So the ph will be equal to the negative log of the concentration of hcl in excess.
00:57
We can calculate that by taking the 40 milliliters, 0 .040.
01:02
0 .0 liters, multiplied by its concentration of 0 .1.
01:08
This will give us moles of hcl that we start with.
01:12
We'll then subtract off the moles of sodium hydroxide that we add, and recognize every mole of sodium hydroxide that we add, will consume, so the negative sign, a mole of hcl.
01:27
We'll then divide that by the new volume, which will be the 40 mil liters plus the 23, or 0 .0.
01:33
0 .063 liters...