(a) Calculate the pH of a buffer that is 0.12 M in lactic acid and 0.11 M in sodium lactate.

Video transcript

Hey everyone. So here we asked calculate the ph of a solution that contains 0.15 Mueller of hipaa Cloris acid. What $0.25 of hypochlorite. They were asked what is the final ph of the solution? If five mL of 0.1 Mueller of hcl solution is added. 2 50 ml of the buffer. Go for a we have a buffer solution which is going to be hcl oh plus cielo minus And this is our weak acid. This is our consulate base. So now we can use the Henderson house about equation to find the ph it's gonna be a ph it was P. K. A. Plus the log of the concentration of the conjugate base. What about the concentration of the week asset U. K. A. Equals negative. Love of the K. A. So it's gonna be a negative log of 3. Times 10 to the -8 P. K. A. 7.4. So we're going to have ph Equal to 7.4 plus the law of 0.2.5 caller Followed by 0. smaller the ph 7.62. And if we're adding hydrochloric acid it's gonna attack the conjugate base Cielo minus. And hcl will lose at H. Plus we're gonna have hcl a quiz Plus Cielo minus. Aquarius. And it's gonna give us H. C. L. O. Please plus cl minus a quiz. And this is gonna be the iron from the strong acid it's neutral. So this will not contribute to the ph And now we need to find the moles of each. We have five ml. And in one millimeter we have 10 10 mega three leaders. And we have 0.1 most of hcl and one leader. And this gives us 0.00 05 moles of hcl. We have 50 ml And one male leader. We have 10 to negative three leaders And we have 0.25 most cielo minus and one liter. We're going to get 0.0125 malls of cielo minus. And then we have 15 ml and one millimeter We have 10 to Meghan three L. We have 0.15 moles of hcl oh in one liter. And this will give us 0.0075 malls of hcl. Oh and we're gonna lose reactant and gain the products so we're gonna have less moles of hcl than everything else. Hcl is going to be completely gone. But we're going to lose the same amount of moles of cielo minus. We're gonna have 0.0125 malls of cielo minus -0.0005 most. And this gives us 0.012 moles of cielo minus. And the psychological basis. And since we're getting product we're gonna gain the same amount for H. C. L. O. We're gonna have 0.0075 most H. C. L. O. Plus 0.5 balls. And this gives us 0.008 Morales of hcl. Oh this is our weak acid. So now we can use the Henderson house about your pleasure to find the ph we're gonna have ph Equals 7.4. That's the law of 0. Divided by 0.0075. And we can use the most for the concentration instead of polarity because you'll get the same answer as dividing most. About 50 ml. It's on a P. H. It's gonna be 7.6. Thanks for watching my video and I hope it was helpful.