1. The pH
Scale

2. Recall that pH is a way to indicate the strength of an acid or a base in terms of the concentration of hydrogen ions. The p stands for ‘potentz’ or strength and the H for Hydrogen. This can be summarized as the [H+ (aq)] in the solution.
It is a logrithmic scale. This means that a difference of 1 unit of pH will change the concentration of H+by 10 times

3. In a neutral solution : H+ (aq) = 1.0 x 10 –7 mol/ L
We can judge the acidity of a solution by measuring the concentration of hydronium ions in the solution.
In a neutral solution : H+ (aq) = 1.0 x 10 –7 mol/ L
In an acidic solution : H+ (aq) > 1.0 x 10 –7 mol/L
In a basic solution : H+ (aq)< 1.0 x 10-7 mol/L
For example, neutrality has a pH = -log [H+ (aq)]
= - log (1.0 x 10-7 )
= 7.0
How do you do this on your calculator when the problem isn't as easy?

4. If an acid has a concentration of 1.57 x 10 -6 M, then what is the pH?
pH = - log [H+ (aq)]
If an acid has a concentration of 1.57 x M, then what is the pH?
The answer should be close to 6 (the exponent involved in the concentration
On your calculator you must press the following:
+/-
Log
1.57 EE -6 then enter OR
1.57 EXP -6
Log
+/-
The answer should be 5.804

5. Let's try another example:
What is the pH of a base with a concentration of 8.54 x M?
pH = -log[H+(aq)]
= - log (8.54 x 10-12) =
What if the pH is known and we want to know the concentration of H+ ?
Then we must do the opposite, which is [H+ (aq)] = 10 -pH
If the pH of a substance is 5.26, then the [H+ (aq)] is calculated as:
[H+(aq)] = 10 -pH
= 10 – 5.26
ENTER 10x then +/- then 5.26 OR
+/ then 10 x

6. Determine the pH of the following substances given the [H+ (aq)]:
a) 1.8 x 10-5 M acetic acid
b) 3.75 x 10-2 M sulfuric acid
c) x M sodium hydroxide
d) 5.55 x M household lye
e) M bleach
f) 8.99 x 10-9 M vinegar
Determine the [H+ (aq)] for the following substances given the pH:
a) milk with a pH of 8.13
b) lemon juice with a pH of 4.34
c) tap water with a pH of 7.861
d) rain water with a pH of 5.76
e) stomach acid with a pH of 2.13
f) chalk with a pH of 10.76