Ephedrine, a central nervous system stimulant, is used in nasal sprays as a decongestant. This compound is a weak organic base: C10H15ON1aq2 + H2O1l2 Δ C10H15ONH+1aq2 + OH-1aq2 A 0.035 M solution of ephedrine has a pH of 11.33. (b) Calculate Kb for ephedrine.

Video transcript

Hey everyone, we're told that pipe perdon is essential in drug production and it is a weak organic base. And were provided the reaction below were asked what is the kB for pie parodied if 0.67 molar solution has a ph of 11.94 1st we need to calculate the concentration of our hydroxide ions in order to do so we can go ahead and take our P. O. H. And we can solve for this by taking 14 and subtracting our ph plugging in those values, we get 14 minus 11.94 which gets us to a value of two point oh six. Now the concentration of our hydroxide ions is going to be equivalent to 10 to the negative P. O. H. Plugging in that value, we get 10 to the negative 2.06. This gets us to a concentration of 8.7096 times 10 to the -3 moller. So as we can see from our reaction above, the concentration of hydroxide ions is equivalent to the concentration of our conjugate acid of our prepared in which is C five H 10 and H two plus. And that's because we have that 1-1 ratio. Now let's go ahead and calculate the concentration of pipe iodine. We can do so by taking our initial concentration of 0.067 moller and subtracting The concentration of our products which was 8.7096 times 10 to the -3 Molar. And this will get us to a value of 0.058 - nine moller. Now to calculate r k B, we know that our KB is equivalent to our products over our reactant. In this case it will be the concentration of hydroxide, ions, times the concentration of the conjugate acid of our pipe iodine, all divided by the concentration of our pipe iodine. And this is at equilibrium plugging in those values, we get 8.7096 times 10 to the negative third. And we're going to multiply it again by 8.7096 times 10 to the negative third. And this will be divided by 0.05, 8 - nine, solving for r k p. We end up with a value of 1.3 times 10 to the negative third and this is going to be our final answer. Now, I hope that made sense. And let us know if you have any questions