bald1
03-19-2006, 05:16 AM
What does pH mean?
The pH scale does seem to be very strange indeed with the way it measures how acidic, or how alkali a given property is. But when you delve deeper as to why the scale is represented this way it does become clear, and I will show you why in its simplest terms.
The term pH can be broken down into two parts:
1) "p"; represents the mathematical symbol for -log (negative logarithm) of the number in question.
2) “H”; represents the chemical symbol for Hydrogen.
The correct way to write this is by using a small "p", and a capital "H". "pH" By changing the way it is written will make it mean something completely different.
For exsample... PH would be abbreviated as a public house.
Ph would mean philosophy as in "PhD" (Doctor of Philosophy).
The pH scale is basically a rough guide as to how many Hydrogen ions are present in any given substance; the more hydrogen ions are present, the more acidic the substance becomes.
Neutral; Acidic & Aklali
pH scale as followed
0.0 through 14.0
-7+
The pH of 7.0 is concidered neutral.
Any solution with a pH below 7.0 ie (6.9 & below) is concidered acidic.
Any solution with a pH above 7.0 i.e. (pH 7.1 & Higher) is concidered alkali
Simply put...
Acidic solutions have a pH between 1 and 6.9 FACT: (your stomach contains HCl and it has a pH of 2.0).
Alkaline solutions have a pH between 7.1 and 14.0.FACT: (your small intestine has a pH of 9.0).
Neutral solutions are neither acidic nor alkaline so their pH is 7.0.
Acids; Hydrogen Chloride; Sodium Hydroxide & Ions
Acids all produce Hydrogen ions (H+). Acids like Hydrochloric acid produce lots of Hydrogen ions; this is because when Hydrogen Chloride gas dissolves in water the molecules of Hydrogen Chloride dissociate into Hydrogen ions and Chloride ions.
HCl = H+ + Cl-
Water also dissociates to produce ions, this time it is Hydrogen ions and Hydroxyl ions.
H2O = H+ + OH-
Sodium Hydroxide also dissociates to produce ions when it is dissolved in water, this time it is Sodium ions and Hydroxyl ions.
NaOH = Na+ + OH-
How to measure/calculate pH using Hydrogen Ions
In each case we can measure or calculate the concentration of Hydrogen ions present. We use the symbol [H+], we use square brackets to mean that it is the concentration of Hydrogen ions.
In HCl Hydrogen Chloride solution or Hydrochloric acid [H+] = 0.01
In H2O water [H+] = 0.0000001
In NaOH Sodium Hydroxide solution [H+] = 0.00000000000001
As you can see, these numbers are very silly; well the first one might be OK but not the second two. So what we do is count the decimal places from the first number, and that is where the pH scale is derived from.
HCl = pH2
H2O = pH7
NaOH = pH14
Recap
..if the pH is low, it means that there is a high concentration of Hydrogen ions.
.. if the pH is high it means that there is a very low concentration of Hydrogen ions or none at all.
The pH scale does seem to be very strange indeed with the way it measures how acidic, or how alkali a given property is. But when you delve deeper as to why the scale is represented this way it does become clear, and I will show you why in its simplest terms.
The term pH can be broken down into two parts:
1) "p"; represents the mathematical symbol for -log (negative logarithm) of the number in question.
2) “H”; represents the chemical symbol for Hydrogen.
The correct way to write this is by using a small "p", and a capital "H". "pH" By changing the way it is written will make it mean something completely different.
For exsample... PH would be abbreviated as a public house.
Ph would mean philosophy as in "PhD" (Doctor of Philosophy).
The pH scale is basically a rough guide as to how many Hydrogen ions are present in any given substance; the more hydrogen ions are present, the more acidic the substance becomes.
Neutral; Acidic & Aklali
pH scale as followed
0.0 through 14.0
-7+
The pH of 7.0 is concidered neutral.
Any solution with a pH below 7.0 ie (6.9 & below) is concidered acidic.
Any solution with a pH above 7.0 i.e. (pH 7.1 & Higher) is concidered alkali
Simply put...
Acidic solutions have a pH between 1 and 6.9 FACT: (your stomach contains HCl and it has a pH of 2.0).
Alkaline solutions have a pH between 7.1 and 14.0.FACT: (your small intestine has a pH of 9.0).
Neutral solutions are neither acidic nor alkaline so their pH is 7.0.
Acids; Hydrogen Chloride; Sodium Hydroxide & Ions
Acids all produce Hydrogen ions (H+). Acids like Hydrochloric acid produce lots of Hydrogen ions; this is because when Hydrogen Chloride gas dissolves in water the molecules of Hydrogen Chloride dissociate into Hydrogen ions and Chloride ions.
HCl = H+ + Cl-
Water also dissociates to produce ions, this time it is Hydrogen ions and Hydroxyl ions.
H2O = H+ + OH-
Sodium Hydroxide also dissociates to produce ions when it is dissolved in water, this time it is Sodium ions and Hydroxyl ions.
NaOH = Na+ + OH-
How to measure/calculate pH using Hydrogen Ions
In each case we can measure or calculate the concentration of Hydrogen ions present. We use the symbol [H+], we use square brackets to mean that it is the concentration of Hydrogen ions.
In HCl Hydrogen Chloride solution or Hydrochloric acid [H+] = 0.01
In H2O water [H+] = 0.0000001
In NaOH Sodium Hydroxide solution [H+] = 0.00000000000001
As you can see, these numbers are very silly; well the first one might be OK but not the second two. So what we do is count the decimal places from the first number, and that is where the pH scale is derived from.
HCl = pH2
H2O = pH7
NaOH = pH14
Recap
..if the pH is low, it means that there is a high concentration of Hydrogen ions.
.. if the pH is high it means that there is a very low concentration of Hydrogen ions or none at all.