00:01
So for this question we have a titration of a strong acid with a strong base.
00:07
So when we look at, we can see that right away both of them are of the same concentration.
00:12
They're both 0 .1 and since it's a 1 to 1 ratio, if i add more of one than the other, then that's the one that's going to be in excess.
00:22
So we can confirm that by taking the first, the hcl, and figuring out how many moles we have.
00:31
So we're going to take our volume, we're going to convert that into liters times its concentration, and that's going to give us the number of moles we have.
00:43
And then we're going to do the same thing with the sodium hydroxide, but this time i have 43 milliliters, so i have 0 .0430 liters times 0 .1 molar, is going to give me 0 .00430 moles.
01:03
So if i can compare these and i can compare them 1 to 1, i know that the hcl is my limiting reactant, so that means that the sodium hydroxide is in excess.
01:17
So that means that my final ph should be greater than 7 because i have a strong base left over.
01:24
So what i have to figure out is how many moles of sodium hydroxide do we have swimming around.
01:29
So since it's 1 to 1, i can just go ahead and take my moles of the sodium hydroxide and subtract from it the moles of the hydrochloric acid, and i'm left with 0 .0030 moles of the sodium hydroxide.
01:58
So now i want to figure out the ph, but to figure out the ph since i have the strong base sodium hydroxide, it's going to be easiest to utilize the poh, which is going to be the negative log of the concentration of the hydroxide ion.
02:13
But i need to find the concentration...