pH is the negative logarithmic scale of the concentration of H+ ions. It is logarithmic because the scale increases by powers of ten (10)
pH = -log[H+]
The negative sign means that pH = 1 has MORE H+ ions than pH = 2.
The logarithmic nature of the scale means that pH = 1 has 10 times more H+ ions than pH = 2.
pH of 7 means that the solution is neutral. There are equal parts H+ ions and OH− ions.
Solutions are said to be acidic if the pH is below 7 and basic if the pH is above 7.
pOH is similar to pH except it measures the concentration of OH− ions. So pOH is equal to negative logarithmic scale of the concentration of OH− ions.
pOH = -log[OH−]
Additionally, pH and pOH must always add up to 14. So they are inversely proportional to each other.
pH + pOH = 14
ex. if pH = 3, then pOH = 11 because 14 - 3 = 11