Calculate the ratio of NaF to HF required to create a buffer with pH = 3.90.

Video transcript

Hey everyone. So here we have an ecstatic asset which is a weak acid. And it's going to associate. And to acetate ion and hydro any um ions and solution. The association constant Acetic acid is 1.78. I'm sent to negative five and it asks if we require a buffer of ph 5.25, what would be the ratio of the conjugate base to the weak asset that we would use? Okay Is 1.78 Times 10 to the - in the ph It's 5.25. And since we're dealing with but first we need to use our Henderson Hasselbach equation and this is going to be ph equals P. K. A. Plus the log of the concentration of the conjugate base divided by the concentration of the weak acid. So we're giving the K. And we need to find the P. K. A. So we're gonna use P. K. A. Equals negative law times K. Eight. So the P. K. A. He goes negative law Times 1.78 Times to the -5. And for P. K. A We're gonna get 4.75. So we're going to get 5.25 Equals 4. plus the law. And we can just call this X. So it's attract both sides by 4. And we're going to get 0.5 equals log of X. So to solve for X We're going to do 10. That is 0.5 power dot exe Which is going to be the concentration of the conjugate base divided by the concentration of the weak acid. It's gonna be 3.16. Thanks for watching my video and I hope it was helpful.