The decrease of one pH unit implies that the acidity is multiplied by a factor of 10. Thus:
- Water with a pH of 6 is ten times more acidic than water with a pH of 7.
- Water with a pH of 5 is 100 times more acidic than water with a pH of 7.
🏾 Contents :
- â… . Definition
- â… . History
- â…˘. pH scale
- â…Ł. How to measure pH?
- â…¤.What is the best water pH ?
- â…Ą. Urinary pH
â—‰ What does pH mean ?
The pH, potential hydrogen, is the measure of the acidity or basicity of a solution. It is a quantity without unit which makes it possible to measure the activity of the hydrogen ion (abbreviated by the chemical symbol H + ) in a solution:
- If the concentration of hydrogen ions in the liquid is high, it is acidic (acids have a pH below 7).
- If the concentration of hydrogen ions is low, it is basic (alkaline) (alkali have a pH greater than 7).
- Substances that are neither acidic nor alkaline (i.e. neutral solutions) typically have a pH of 7.
The pH scale is used to determine the degree of acidity of a substance. It is divided into levels from 0 to 14, 0 being the highest degree of acidity while 14 is the highest degree of alkalinity.
â—‰ History : weight of hydrogen or hydrogen potential?
In 19092, the Danish chemist Søren Sorensen , who worked on the effects of the concentrations of a few ions on proteins during the processes beer making, notices the importance of hydrogen ions and decides to introduce the concept of pH.
â—‰ pH scale
The pH scale is used to classify solutions in terms of acidity or basicity (alkalinity). This scale is based on the balance between hydrogen ions [H+] and hydroxyl ions [OH-] :
- If the concentration of H+ is higher than that of OH-, the material is acidic; that is, the pH value is less than 7.
- If the OH concentration is greater than its H+, the material is basic, with a pH value greater than 7.
- If equal numbers of H+ and OH ions are present, the material is neutral, with a pH of 7.
The pH scale is often said to run from 0 to 14, and most solutions fall within this range. However, very strong acids can have a negative pH, while very strong bases can have a pH above 14.
| Substance | pH range | Type |
|---|---|---|
| Battery acid | <1 | Acid |
| Stomach acid | 1.0 - 1.5 | |
| Vinegar | 2.5 | |
| Orange juice | 3.3 - 4.2 | |
| Black coffee | 5 - 5.03 | |
| Milk | 6.5 - 6.8 | |
| Pure water at 25°C | 7 | Neutral |
| Sea water | 7.5 - 8.4 | Base |
| Ammonia | 11.0 - 11.5 | |
| Bleach | 12.5 | |
| Detergent | 13.0 - 13.6 |
â—‰ How to measure pH?
Le pH peut être mesuré électroniquement ou visuellement. Il existe deux principales méthodes couramment utilisées :
- Rough, simple, and quick measurements of pH can be made using litmus paper or another type of pH paper known to change color around a certain pH value. These indicators have precision limitations and can be difficult to interpret correctly in stained or turbid samples.
- More accurate pH measurements are obtained using a pH meter. it works by measuring the potential difference between a hydrogen electrode and a standard electrode.
â—‰ What is the best water pH ?
Water with a very low or high pH can be a sign of chemical pollution or heavy metals.
The best drinking water pH is right in the middle at 7. The United States Environmental Protection Agency recommends that the pH level of water sources be at a level of measurement pH between 6.5 and 8.5.
â—‰ Urinary pH
Normal urinary pH is slightly acidic, common urine pH value is 6.0-7.5 for most people, but normal range is 4.5-8 ,0.