Calculate 3OH-4 and pH for each of the following strong base solutions: (c) 10.0 mL of 0.0105 M Ca1OH22 diluted to 500.0 mL

Video transcript

So in this video we're going to figure out how to calculate for the hydroxide ion concentration as well as a ph of a solution. So first things first, let's go ahead and write out the chemical equation for our sodium hydroxide. So when it's diluted into water is going to go ahead and associate into its ionic forms. So first we have our N. A. O. H. Of course that's going to go ahead and associate into an A plus and a minus. Okay, second, we see the key word here, we have the word diluting. So we're gonna go ahead and use our dilution formula and that is going to be M one V one equals two M two. V two. So M one is going to be 0.0225. And then our V one is going to be 15 ml. Our M. Two and V two. Now M two is going to be our unknown. Which we are solving for A and R. V two is going to be mL. Now we're solving for M. Two here, so we can go ahead and first rearrange this equation to go ahead and make it easier for us. So if we're solving for M. Two, I'm gonna go ahead and isolate this by dividing each side by V. Two. If we do that we'll get the equation M two is equal to And one times v one all over v. two. Okay, now we're simply just going to go ahead and plug in. The numerical values sir. M one we said was to be 0.225 moller RV1 is 15 mm And it's going to be all RV to which we said is 545 ml. We can see for our units that the millions will go ahead and cancel out leaving us with just the unit of concentration, which is what we want. So putting these values into my calculator, I will get the value of 0. moller. Alright, so now that we have that we can go ahead and actually solve for the concentration of our hydroxide, how we can do this is let's use a different color here. So the concentration of our hydroxide is going to equal to Let's see here first we have what we just saw for which is the concentration of the solution. So that's going to be 0.00061926605. And that's going to be moles her one liter. Okay, so we're gonna go ahead and now use our chemical equation and stock geometry, we know that what we saw for earlier, this was for our moles of any O. H. So to cancel out the most of any O. H. We'll go ahead and put that and the denominator And we are solving for the moles of hydroxide. So that's 1-1 ratio according to our chemical equation. We can see here that my moles of NH are going to go ahead and cancel out leaving us with the units of moles of O. H. Over leaders, which is the concentration of R. O. H value. So putting these numerical values into my calculator, I'm going to go ahead and get 6.19 times 10 to the -4 moller. Okay, so that's going to be one of my answers and that is the concentration of my hydroxide now scrolling down a little bit to give us a little bit more room to solve for our P. H. So first, now that I have or what we just saw for is our concentration of R. O. H. We can actually first solve for P. O. H. So the equation for P. O. H is the negative log of the concentration of our hydroxide, which is what we just saw for. So P. O. H is going to equal to the negative log of 6.19 times 10 to the -4, plugging that into my calculator. My p. o. h value is going to be 3.208. That's all for my ph My PH is equal to 14 -3.208. So why I'm using this 14 values because we know that the ph the maximum ph will be 14 and then this is going to be my P. O. H. So 14 minus this will give us our ph level. So putting that into my calculator again, my ph value is going to be 10.792 and that's going to be my second answer for this problem. Again, we have the concentration of our hydroxide to be 6.19 times to the negative four, and my ph of the solution is 10.792. Thank you all so much for watching.