A mixture is made using 50 ml of 0.20M NaOH(aq) and 50ml of water. at 25 degree C.. what is it pH?

Question

a mixture is made using 50 ml of 0.20M NaOH(aq) and 50ml of water. at 25 degree C.. what is it pH?

i just took the log of 0.20 and i get 13.30.... isnt this right?

2. what is the pH of a 1.00 x 10e-9 molar solution of HCL?

the answer i get for this one is 9 but my friend think its 7.. we both are confuse... can someone help us thanks

Answer 1

pH = -log [H+], and pH + pOH = 14

For the first question, 0.2 M NaOH = 2x10^-1M and so the [OH] = 1- log 2 = 0.7;  pH = 14 - 0.7 = 13.3.  So you got the right answer, but not by just taking the log of 0.2.

For the second question, your answer is correct.  The ph = 9.