A 30.0-mL sample of 0.165 M propanoic acid is titrated with 0.300 M KOH. Calculate the pH at each volume of added base: 10 mL.

Video transcript

Hi everyone here we have a question asking us what is the ph of the solution of 25 mL of 0.158 Mueller Ben's OIC acid high traded with 10 mL of 0.145 molar sodium hydroxide. So R. K. A. of benzoate acid equals 6. Times 10 to the -5. And now we need to calculate our number of moles. So we have 25 ml times one leader Over 1000 mill years, Times 0. moles over one liter. And our middle leaders are canceling out and our leaders are canceling out and that equals 3. Times 10 to the -3 moles a Benz OIC acid. And next we have 10 ml times one liter Over million years, times 0.145 moles over one liter. And our middle leaders are canceling out and our leaders are canceling out. And that gives us 1.45 Times 10 to the negative 3rd moles of sodium hydroxide. Now we need to make an ice chart. So we're gonna let H. A. Stand for Ben's OIC acid and a minus stand for its conjugate base. So we have H A. Plus hydroxide goes back and forth between its conjugate base plus water. And we're going to have our initial our change and our end. So for Ben's OIC acid, our initial is 3.95 Times 10 to the -3 moles For hydroxide, it is 1.45 Times 10 to the - moles for its conjugate base. We are starting off with zero and for water it doesn't matter because it is a liquid and not acquis. So our change in Ben's OIC acid is one negative 1.45 times 10 to the negative three moles for hydroxide, it is negative 1.45 times 10 to the negative three moles for its conjugate base. It is plus 1.45 Times 10 to the -3 moles. So our ending is 2.5 Times 10 to the -3 moles, zero and 1. Times 10 to the -3 Mnolds. Now we use our Henderson Hasselbach equation. So ph equals P. K. A. Plus the log of the concentration of our conjugate base times the concentration of Urban's OIC acid. So P. H. Equals the negative log of 6.4. 6 Times 10 to the - plus The log of 1.4.5 Times 10 to the -3 Divided by 2.5 times 10 to the - Equals 3.95. So our final answer here is 3.95. Thank you for watching. Bye