What is pH?

What does pH stand for?

In simple language:

pH stands for the power of hydrogen. pH is defined as a unit or measure to show the concentration of hydrogen ion (H+). When the pH is 7, the solution is neutral. In other words the concentration of H+ is equal to the concentration of OH-.

Solutions with pH lower than 7 are acidic. Solutions with pH higher than 7 are alkaline.

The pH in strong acids is 0. The pH in strong alkalis is 14.

To be more technical:

 

 
pH - what it means. - Log (Base 10) of [H+] in Mol/L
The pH is the negative logarithm of the hydrogen ion concentration. A complete definition requires that the logarithm is defined as being to the base ten and the concentration be measured as activity in moles per liter. Confusion arises because, as the acidity increases, the pH decreases. To avoid mistakes when discussing acid-base balance, it is often safer to avoid "increase" and "decrease" and use "more acid" and "more alkaline" instead.

To understand logarithm, think of "power." Thus 103 = 1000 and log (1000) = 3. When the pH changes by 0.3 units, e.g., from 7.4 to 7.1 the hydrogen ion concentration doubles (from 40 to 80 nMol/1). Wouldn't [H+] be so much easier to understand?

 
Logarithm. Log (1000) = 3
Logarithm is another source of confusion in acid base balance and is responsible for the mistaken impression that the body maintains remarkably tight control over its hydrogen ion concentration - it doesn't. (Blood pressure or pulse measured with a logarithmic notation would appear equally stable). To remember how to understand logarithm, think of "power." Thus 103 = 1000 and log (1000) = 3. When the pH changes by 0.3 units, e.g., from 7.4 to 7.1 the hydrogen ion concentration doubles (from 40 to 80 nMol/1). Wouldn't [H+] be so much easier to understand? 


pH CALCULATOR

This program will calculate the pH of a solution of known concentration.

Enter the name of the chemical in solution
(if it is an acid be sure to include the word "acid" in the name).

There are different ways to enter the concentration of the above acid:

  1. If known, enter the concentration for your application directly
  2. If the chemical is a solid, enter the weight of the chemical and the total volume of your application.
  3. If the chemical is a liquid, enter the volume of the chemical, its concentration, and the total volume of your application.


1. Enter the concentration (Molarity) of the chemical

2. Alternately, enter the weight (in grams) of the acid or base being added to the solution.

and the total volume (in liters) of the solution (water plus the acid or base).

3. Alternately, enter the concentration of the chemical being added to your application (in molarity or normality as it appears on the container).

the volume (in liters) of the acid or base being added to your application.

and the total volume (in liters) of your application (including the amount of chemical being added).

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