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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

Science class

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Acidic and basic solutions

pH of aqueous solutions
Ions in acidic and basic solutions
Dilution of acids and bases
Composition of hydrochloric acid
Chemical reaction between iron and hydrochloric acid

Electrochemical cells and chemical energy

Chemical reaction beteween a copper sulphate solution and zinc
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