Drops of NaOH vs. pH151411PH10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 Drops of NaOH95 100 105 110 115 120...

Calculate the pH of a $1.0 \times 10^{-7}-M$ solution of $\mathrm{NaOH}$ in water.

Let's calculate the pH of the 1.0 times 10 to the negative seven Moeller anyway, pollution and water. So any weeks were given its 1.0 times 10 to the negative. Seven. Moeller, which means the hydroxide and hilarity. Physical 1.0 times. 10 Mega seven Moeller This is in water. So two h 20 in equilibrium with H plus Okay, and each minus Is that a brace table here and all rights table. We're gonna have 1.0 times 10 to the negative seven. That's from the drug, said any a witch plus x x x 1.0 times 10 to the negative seven plus X We have our K W expression here, which is equal to each 30 plus times each minus 1.0 times 10 to the negative. 14 for the X 1.0 times 10 to the negative seven plus X Solving this for X. We get 6.2 times 10 to the negative eight there for the each three oo plus similarity is 6.2 times 10 to the negative eight Smolar and the pH is negative. Logs 6.2 times 10 to the negative eights and solving for the pH. Here we gets pH. That's equal to 7.21

So now work on problem 94 from chapter 17. In this problem, we're asked what is the pH of the solution made them Maxine 0.30 moles and a wage Sierra 0.25 goals and a two h appeal for and 01 to 0 moles of H three Pio for with water and I leading to one leader. So here what we need to realize first is what form the phosphate molecules will be in the phosphate compounds will be in. So initially we have 0.20 moles of H three p 04 and this will be converted 20.20 moles of H to peel for minus by the hydroxide but were told that we add zero point zero 0.3 moles of anyway. So we have 0.1 miles left. So part of this age to Pio for here is your 0.10 moles will now be ah converted two 0.10 moles of H P o for two minus so left over. So left over We now have 0.10 moles of h u p o for and we also have in addition to what? We had it at the beginning, so we had 0.250 point one. So 0.35 goals of the H P O for two months now the K a for this, uh, transition here from H. To be afford HBO for is equal to 6.2 times 10 to the minus eight. So pH will be able to p k, which is 7.21 plus the log of base over acid, which in this case is there a 0.35 divided by 0.0. So we get a value equal to once we do this calculation 7.75

This question here asked us about the pH of the in a different n a o h solutions of different concentration. And so to answer this question, we need to know that records the N a. O. H. Is a very strong case. And so that means it's going to disassociate completely 100% almost up into any a plus. And oh, it's finest. And so the first, ah, concentration were checking is one Moeller. Pardon me, one Moeller and a wage. And so that means that we're going to get a concentration of which minus, which is equal to one muller. And so P. O. H can be calculated as the negative log of the concentration of O H. Minus, which, if you plug one Moeller and will be one. And we need to remember that pH plus p o. H equals 14. If p o. H equals one Ph. Eagles 30 and that's dance for the first part. The second part asked us, What if we have one times tense? The negative 10th Moller and I O. H. And you might be tempted to just do the exact same thing. Plug in negative log of tense, a negative 10th equals P O h. But when you see remember here is that the concentration of O. H minus? Um, in h 20 just sitting Ambien. Lee is already tense. The negative seventh. That's something we know from the auto ionization of water. Remember that two H 20 molecules become O H minus plus H 30 plus. Because of this, there is already a concentration of tense. The negative seventh of o H mines tense today of 10 is so much smaller than that that really are concentration of which minus is attends the negative seventh apartment negative seventh and that is equal to the P o age, which is usually seven. Um which means that the pH is also your seven. Be careful for these for these very small concentrations, most the time this tense the negative seventh is not relevant, but we're only working with this. It will become, and finally we are given a two Moeller cod in a o. H solution asked to find the ph of it and, um, the same processes in part one can be done. And so we know that p o. H will equal be negative log of the constellation of O H minus, which, because all two molars of this are going to become a witch minus and an A plus. That means we're taking the negative log of to and what you're going to get is a negative number. You're going to get negative 0.301 And don't be worried about this. This is something we've discussed earlier that the, um ph or P O. H can be night is just unusual because most of things we work with are weak acids, air bases and don't associate all that way. But we can still use the same concept that P O H. Close PH equals 14 and from that will get that pH here is equal to 14.3, and that's the final answer.

The pH of a solution that has a concentration of sodium hydroxide at 1.2 times tend to negative five We'll also that will be a result of the fact that the hydroxide concentration is also at a concentration of 1.2 times 10 to the negative five. Because this is a strong base that completely dissociates. So we can calculate the pH by taking the negative log of the hydro Nehemiah in concentration. But we don't know that directly. We just know the hydroxide concentration. So to get the hydro knee, um, concentration will divide the hydroxide concentration 1.2 times tend to negative five into K W. K. W has a value of 1.0 times 10 to the negative 14. This then gives us our hydro name concentration. We take the negative log of that to get pH and we get 9.8 The answer is C