A 25.0-mL sample of 0.125 M pyridine is titrated with 0.100 M HCl. Calculate the pH at each volume of added acid: equivalence point.

Video transcript

Hi everyone here we have a question asking us to calculate the ph at the equivalence point for the tight rations of a 75 millimeter sample of 0. moles of ethyl amine with 0.12 molars. Romick acid. So first we need to calculate the moles. So the moles of the base is going to equal the molds of the acid is going to equal the moles of ethyl amine. It's going to equal 0. moles per liter Times. l Equals 0. moles. Now we need to calculate the volume of bro make acid used. So our mole of ethyl amine equals the moles, A bro, make acid Equals 0. moles. The volume of chronic acid Equals 0.0159 moles Divided by 0.1-0 moles per leader Equals 0. L. So now we need to calculate our polarity. So our concentration of ethyl amine Equals 0. moles Over 0.1325 l Plus 0.075 l Equals 0.0766. More clarity. Now we need to set up an ice chart. So we have our ethyl amine plus water forms are conjugate base plus H 30. Now our water isn't going to matter because it's a liquid and then we're going to do the initial the change and the end. So our initial for ethyl amine is going to be 0.0766. Our conjugate base is going to be zero and r H 30 is going to be zero. Our change is going to be minus X and plus X and plus X. Our end is going to be 0.0766 - X. And X. So our KB Equals 5.6 Times 10 to the Negative Ford. R K A equals S element Times H times are conjugate base are divided by our conjugate base. So K W divided by K. V equals that's what I mean, Times H divided by our database. So 1.0 Times to the -14 Divided by 5.6 times to the negative ford X squared Divided by 0.07 6, -1. So 1.79 times to the native 11 equals x squared Divided by 0. minus six. And we need to check if X is knowledgeable in the denominator. 0.766 divided by 1.7 times 10 to the negative 11 equals 4.29 times 10 to the ninth which is greater than 500. Maybe it is negligible. So X equals the square root. 1.79 Times 10 to the - Times 0. equals one 0.17 Times to the Native six smaller X equals our concentration of H 30 plus, Which equals 1.17 times to the -6 military ph equals negative log of the concentration of H equals negative blog, as 1. Times 10 to the negative 6th polarity Equals 5.93. And that is our final answer. Thank you for watching. Bye.