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Acidic and basic solutions
pH of aqueous solutions
1) What is pH ?
Acidity is a rather familiar concept because many foods and drinks are acidic in varying degrees: vinegar, lemon juice, tomatoes, citrus fruits etc..
Unlike acidic solutions there are basic solutions. It is difficult for us to understand what is a basic solution because food and beverages are almost never basic. There are basic solutions among cleaning products like bleach or detergents.
The pH is a number that indicates whether a solution is acidic or basic and with what degree.
The pH is a chemical variables that have no unity.
2) How to measure pH ?
The pH can be measured using pH paper:
It consists of strips soaked with chemicals that take different colors depending on pH.
A drop of solution must be placed on a strip. Comparing its color to a color index, we can deduce the pH value.
Comment: a pH paper gives only an approximate value of the pH to the nearest unit.
The pH of a solution can be measured using a device called a pH meter.
It consists of a probe (itself consists of electrodes). Once this probe is immersed in a solution, the pH meter shows the pH value.
The pH meter provides a quick and accurate measurement (usually to the nearest tenth).
3) pH of acidic and basic solutions
- If the pH is between 0 and 7 then the solution is acidic.
The lower the pH is, the more acidic the solution is
- If the pH is between 7 and 14 then the solution is basic.
The higher the pH is, the more basic the solution is
- If the pH is 7 then the solution is neither acid nor basic, it is said to be neutral
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