I need help with PH and PoH Problems...?

Question

Egg whites have an hydroxide ion concentration of 3.3 x 10–7 mol/L. The hydrogen ion concentration in egg whites is...

** the answer is 3.0 x 10-8 mol/L, but i dont know how to get this...

Answer 1

take the log of this [OH-]..

then add 14.

then raise 10 to the negative of this answer.

Answer 2

There is an interesting relationship between [H+], [OH-], and pH. Recall what you know about acid-base chemistry. A Bronsted Lowry acid is a substance that donates H+ and a Bronsted Lowry base is a substance that accepts H+. However, there are some substances (like water) that can act as either a Bronsted Lowry acid or a base.

H2O + H2O <=> H+ + OH-

This reaction is called the autoprotolysis of water and the equilibrium constant (kw) equals 1 x 10^-14.

kw = [H+][OH-]

So in pure water we can always find the concentration of either species if the concentration of the other is known because the product of [H+] and [OH-] is constant.

So to answer your question:

[H+][OH-] = kw

[H+] = ({kw}/[OH-]) = ({1 x 10^-14}/{3.3 x 10^-7 M}) = 3.0 x 10^-8 M

pOH is -Log[OH-]

some people like to do it like this:

pOH + pH = 14

pOH = 14 - pH