Calculate the pH of the following solutions.
a. 5.00 g of HBr in ...

Question

Calculate the pH of the following solutions.
a. 5.00 g of HBr in 100 mL of aqueous solution
b. 1.50 g of NaOH in 50 mL of aqueous solution

Accepted Answer

Hey everyone. Let's solve this problem. It says two solutions were prepared by one dissolving three g of hcl in 200 mils of equity solution and to dissolving three g of N A. O. H. In 100 mils of equity solution determine the ph of each solution. So how do we find ph well let's recall some important equations. We have P. H. Equals negative log of the concentration of H. Plus ions. And if we're going from a base we could calculate P. O. H. Which is the negative log of the concentration of O. H minus ion. And if we have P. O. H we can calculate ph because those total to 14. So we can just subtract. Also. We're working with H. C. O. In N. A. O. H. Which are a strong acid and strong base respectively. So it's important to remember that in this case the concentration of the strong acid hcl will equal the concentration of the H plus ion. Because it fully dissociate right, Hcl will fully dissociate to H. Plus and cl minus and similarly when we have a strong base like N. A. O. H. The concentration of the strong base will equal the concentration of the O. H. Again like N. A. O. H will fully dissociate into N A. Plus and O H minus. Okay so with this being said we were given the amount of hcl and how much weigh solution it's dissolved in and same for the base. So we can calculate the concentration of our strong acid and strong base in. And what unit do we use for concentration moles per liter. Right so we're given grams per meal leader so we'll have to convert those in order to calculate the concentration. Then we can use the equations that I just laid out to calculate P. H. Or P. O. H. Right? Taking the concentration solving for P. H. Or P. O. H. And if we found P. O. H. We will then have to calculate ph right. Using that last equation. And again that's only if we're using P. O. H. Okay so let's do this. So let's start with Hcl first. So like we said we need to calculate the concentration in moles per liter. So let's convert three g to moles first. So three g of H. C. O. The molar mass of each C. O. is 36. 4606 g in one mole. And that will give us .00.0823 moles of H. C. O. I cannot write today. And then our 200 ml more. We will convert to leaders. So we have 1000 ml in one leader Giving us .2 leaders of solution. So dividing our most by our leaders will get our concentration. So if we divide those moles over leaders that gives us .41 to Mueller H. c. o. Okay that's the concentration. And like we said since this is a strong acid, that concentration of the hcl will equal the concentration of the H. Plus ion. Okay so now we can use this in our ph equation. Right? Since it's H. Plus we can go straight to our P. H. Equals negative log of H. Plus which will be 0.412 here. And if you plug that into the calculator you will get ph of hcl solution Is 0.385. Okay. Alright. Let's do our second solution which is now basic. So we have to do a little bit differently. Right? We're going to calculate P. O. H. But same first step. So we're starting with converting our grams to moles three g of any ohh. And in one mole of video each we have 39 0. g of any O. H cancel our units diagonally. That gives us .0750 moles Video. 100 ml of solution. We have 1000 Middle leaders and one leader giving us point 0. leaders. And dividing these values will get our concentration .0750 malls over .1 l Equals . Mueller N. A. O. H. And now we will plug that into our Well this is also the concentration of the O. H. Ion right .750. And now we can plug that into our P O. H. Right? P. O. H equals negative log of 00.750. And then that will give us A value of .125. And then, using our last equation, we know that p o H Will Equal 14 -125, giving us 13. as the pP of the n a o H solution. That's it for this problem. I hope this video is helpful, and thanks for watching.

Calculate the pH of the following solutions. a. 5.00 g of HBr in 100 mL of aqueous solution b. 1.50 g of NaOH in 50 mL of aqueous solution

Watch next