Consider the titration of a 35.0-mL sample of 0.175 M HBr with 0.200 M KOH. Determine each quantity. c. the pH at 10.0 mL of added base

Video transcript

Hello everyone today we are being given a parliament asked to solve solve it. So you have a 25 millimeter sample of a 250.15 molar hcl 04 is being tight traded against a 40.117 moller N. A. O. H. Solution. What is the ph of the mixture when 30 mL of the base has been added. So the first thing we wanna do is we want to find the number of moles of each component. We'll start with H C. L. 04. And so by doing that we'll take 25 mL will convert that to leaders. And we can say that one middle leader is equal to one times 10 to the negative third leaders. And then to get rid of leaders we can say that one leaders equal to 0.15 moles of h C. L. 04. This is gonna give us 0.00375 moles. And we'll do the same thing for any O. H. We'll take the 30 mL will convert that to leaders using the conversion factor and then we'll we'll also get rid of leaders by multiplying by the polarity. And so that will be 0. moles of N A. O. H over one leader. And that's gonna give us 0.351 moles of N A. O. H. Next we must fill out our ice chart. And so that's gonna be I C. E. And so we'll have any O. H. S. The first compound here we'll say plus H C. L. +04. Now it's gonna give us in a. C. L. +04 plus pure water for any O. H. Our initial concentration of it. Our initial number of moles is 0.375 for hcl of four. So the initial moles of any O. H. Is 00351. And for H. C. L. 04 it is going to be 0.375. And of course we don't have any initial concentrations of water or sodium cielo four. However we have to subtract from the least number of moles. And so that's why we say -0.00351 for both of our react mints. But then we go we're gonna go ahead and add those equivalents those number of moles to our products. And so when we do that we're gonna end up with zero moles of any O H 0.0 to 40 moles of hcl 04. And then we're gonna have 0.351 moles for both water and sodium Cielo four. And so now we just have to calculate the polarity of H. C. L. 04 and then use it to find the ph and so we'll say the total volume of the solution is going to be 25 mL plus r mL. To give us 55 mL. And so to find the concentration of h. c. l. 0. 4. we're gonna take our moles that we formed. So 0.0 to 40 moles of H. C. L. 04. And then we're going to divide that. We're gonna have that over our 55 mL. And of course we want leaders. So we have to use a conversion factor that one millimeter is equal to 10, 10 to the negative third. Leaders. And we do that. We end up with familiarity of 0.436 molar. Now since hcl hcl 04 is a strong acid, its concentration will be equal to the number of protons that we have. And so to find a ph you see the ph is equal to the negative log of our H plus ions. So it's gonna be negative log is equal to 0.00436. So we're gonna have a final ph of 2.360. I hope this helps ahead until next time.