What is the pH of a 0.025 M solution of NaOH?

A. 2.50
B. 1.60
C. 12.40
D. Cannot determine without the Kb of NaOH

Question

What is the pH of a 0.025 M solution of NaOH?

 		A.	2.50
 		B.	1.60
 		C.	12.40
 		D.	Cannot determine without the Kb of NaOH

vera_ewing · Answer

@taramgrant0543664

photon336 · Answer

0.025 = [OH]

[OH][H+] = 1x10^-14

(1x10^-14)/(0.025) = 4x10^-13

-log(4x10^-13) =12.4

taramgrant0543664 · Answer

For this one you solve the same way that you normally would and add an extra step at the end since it's OH 
To start we use the formula:
pOH=-log[OH]
=-log(0.035)
=1.602
Since it's asking for pH and not pOH we just do a simple subtraction:
pH=14-pOH
=14-1.602
=12.398

vera_ewing · Answer

Thank you! That makes so much more sense now! :)

taramgrant0543664 · Answer

No problem!!

photon336 · Answer

Explanation:

You're given the concentration of OH- which you need to use to find the pH
pH = -log(H) which p means take the -log of something.

At 25 degrees Celsius you know that the [H][OH] = 10^-14 so if you know the concentration of one you know the concentration of the other.