Question

Solution equals 0.015 M HCl
Find OH
Find pH

Isn't pH=1.8?
I don't know how to find OH :(
Is there a formula or do subtract 14-1.8?
I'm confused and I got this assignment today yet we haven't gone over anything yet.

Answer 1

I would not round from 1.82 for pH of 0.015 M HCl. In logarithms the 1 of 1.82 just tells you the location of the decimal point in the 0.015 number so that counts as only two significant figures in 1.82

you can get OH either of two ways.
pH + pOH = 14 and after you know pH you solve for pOH, then convert to OH by pOH = -log(OH^-).
OR you can do
(H^+)(OH^-) = Kw = 1E-14.
You already have H^+ in the problem and you can convert directly to OH this way without going through pH and pOH step.

Answer 2

1. OH= 6.67 *10^-13
Here's what I did
1*10^-14/0.015 M= 6.67*10^-13
2. pH=1.82

Did do it right? Wrong?
Thank you so much for all your help I really appreciate it :)

Answer 3

All of that looks ok to me.