Calculating pH of Buffered Solutions: Do You Need a Ka/Kb Value?

[Dpasi314]

Hello,
So as the end of the year comes to an end, AP Chemistry is getting increasingly more difficult to the point where I don't understand anymore. In our homework there is a questions asking to calculate the pH of a buffered solution. The only information it gives you is the chemical formula and the molarity. i.e
Calculate the pH of each of the following buffered solutions:
a. 0.50 M C₂H₅NH₂/0.25 M C₂H₅NH₃Cl

I'm not quite sure how I'm suppose to be able to figure out the pH without having a Ka/Kb value given? Is the question assuming that I need to know what the Ka/Kb value? Or am I missing something entirely?

Thanks for the help!

 

[Chestermiller]

Hi Dpasi314. Welcome to Physics Forums.

Do you know the name of the 0.5 M species? If so, have you tried Googling it? It should take less than a minute to find the Kb.

Chet

 

[Borek]

Perhaps you were given a pKa table? Or there is one in your book?