Course:MATH110/Archive/2010-2011/003/Teams/Aargau/Homework 13
The pH level determines how acidic a liquid solution is. It is a important tool to use in any science, especially biology. Water has a neutral level of pH at 7.0. Anything with a pH level lower than 7 is acidic, and anything with a higher level is basic.
Like the Richter scale used to measure earthquakes, the pH scale is logarithmic. When we say a pH scale is logarithmic it means a difference of one pH measurement unit represents a tenfold, or ten times increase or reduction of hydrogen ion activity in the solution.A low pH indicates a high concentration of hydronium ions, while a high pH indicates a low concentration. This explains how a solution’s aggressiveness increases with the distance from the neutral point. The pH scale is a logarithmic scale which extends over 15 orders of magnitude, measuring the concentration of H ions in a solution. pH 0 is 10,000,000, De-ionised water is pH 7, 1 and pH 14 is 1/10,000,000
The pH equation is as follows:
pH=-log(H+) where H+ is ion concentration
We can rewrite this equation to look like:
H+ = 10^(pH)
This is where we can see that the pH is actually an exponent, explaining why the pH scale is logarithmic. The result of the scale being logarithmic is that there are huge differences between the pH levels. A liquid with a pH level of 5 is 10 times more acidic then a liquid with a pH level of 6.
On a calculator, the antilog or 10^x button is used when you are converting from pH back to H+so if the pH=5.3you would enter -5.3 in the calculator and hit the 10^x button this would enable you to find out that [H+]=0.000005 M or 5 x 10^-6 M
in general terms, we can define pX=-log10[X]
log (A x B)= log A + log B
with this equation in chemistry there is the formula known as the ion product which is as follows:Kw=[H+][OH-]
this can be rewritten as a logarithm log Kw = log[H+][OH-]
-log Kw= -(log[H+][OH-])
pKw=pH+pOH
if Kw=10^-14 then pKw=14=pH+pOH