# chemistry

posted by
**Abigail** on
.

Please let me know if my answer to the following question is correct.

Question:

What is the concentration of a weak base if its Kb = 1.4 x 10-11 and its pH = 8.75?

Answer:

Converting pH to H^+ concentration using the formula H^+ = 10^-ph, therefore 10^-8.75 gives an H^+ concentration value of 1.0 x 10^-9. Now, using the formula Ka=Kw/Kb and subsitituing in the values (Ka = 1.4 x10^-14/1.4 x 10^-11) gives 1.0 x 10^-3.

Now, subtracting 1.0 x 10^-3 from 1.0x 10^-9 gives a concentration of 9.9 x 10^-4 mol/L