Base and Acid 01 ← →
Describing Asids and Bases:
We can use an wquilibrium constant to find the concentrations of H3O+ and OH- in acid/base solutions.
This constant, Kw, is called the ion product constant for water. In general; Kw = [H3O+][OH-]
At 25, Kw = 1.0x10-14
* If given the concentration of either H3O+ or OH-, we can find the missing concentration
EX: Find H3O+ and OH- in 0.45M HCl.
Using pH...
The range of [H3O+] can be very large. To overcome this problem we work with logarithms.
pH can be defined as -log[HSUP>+] or pH = -log[H3O+ ]
In neutral water at 25
[H3O+] = 1.0 X 10-7
pH = -log[H3O+] = -log[1.0 X 10-7] = 7
Similar to pH, we can also describe [OH-] by using pOH:
pOH = -log[OH-]
* Remember that;
Kw =[H3O+] [OH-] = 1.0 X 10-14
taking -log of both sides....
= pH + pOH or pH + pOH = 14
A logarithm of number is the power to which you most raise 10 to equal that number.
We can also find [H3O+] and [OH-] by finding the antilog of this pH or pOH.
[H3O+] = 10-pH
[OH-] = 10-pOH
* on your culculator, use 10x button!
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