The pH of SOLUTION 

  pH is a measure of the acidity or alkalinity of a solution. It's calculate using the negative logarithms of the hydronium ion concentration. To calculate pH, you need the concentration of hydronium ions in moles per liter (molarity).

 Hydronium ions : acids donate H+ ions, which combined with water molecules to form.

Logarithms : the logarithms (log) tells you the power to which a base (usually 10) must be raised to produce a given number.

PH scale: the pH scale range from 0 to 4. A pH of 7 is neutral. Values below 7 are acidic and values above 7 are base(alkaline).

PoH: is a related scale that measures the alkalinity of a solution. PoH+pH=14

Strong VS Weak Acids/Base 

Strong acid and base completely dissociate in water while Weak Acids and base only partially dissociate. This affect how their concentration are used in pH calculation 

Example: Strong Acid 

If you have a solution of 0.055M HBr(a strong acids), the pH is -log(0.055)=1.26

Strong Base 

If you have a solution of 0.0035M LioH(a strong base), you would first calculate the PoH(-log (0.0035)=2.46) and then substrate it from 14 to get the pH(14-2.46=11.54)