Hwmk 2 Achieve Question 5

[Daljit Takher 1B]

The Kb for an amine is 7.204×10−5. What percentage of the amine is protonated if the pH of a solution of the amine is 9.378 ? Assume that all OH− came from the reaction of B with H2O.

I found BH+ using the given pH but how do you find B using BH+?

[Ben Zhang 2H]

If you're talking about concentration, then you use the concentration you found of BH+ and OH- to find the concentration of B. Since H20 is a liquid, it isn't used to find the equilibrium constant. As a result the equilibrium constant is equal to ([OH-]*[BH+])/[B]. The equilibrium constant is already given so you just plug the values in and solve for [B].

[Shivani Sakthi 1l]

First, it is important to consider that the amine is being protonated, meaning that a proton is added to a compound. Since the amine is accepting a hydrogen, according to the Bronstead Lowry Acid and Base laws, we know that amine is a base because it accepts a proton from H20 to make OH. So, it is important that using the PH, you find the pOH of the solution is amine is basic.

TO OBTAIN PERCENT IONIZATION, you need the initial concentration of amine and the concentration of protoneated amine. Right now, We know that amine is a strong base, therefore, we can assume that the acid completely dissociates. So concentration of OH-= concentration of protoneated amine. All we need is the initial concentration of amine or B. To do this, you set the Kb value equal to [OH-][BH+]/B and solve for B.

Now we have all the needed values. to find percent ionization, divide the amount of protoneated amine by the sum of protoneated amine and neutral amine (formal concentration). This will give you the percent of amine protoneated .