Some bases are found in the substances used in our daily lives:
- magnesium hydroxide (Mg (OH)2), present in milk of magnesia used to combat stomach acidity;
- hydrated lime (Ca (OH))2), used as mortar in civil construction;
- sodium hydroxide (NaOH), used for material cleaning, pipe unclogging and widely used in industry;
- Ammonium hydroxide (NH4OH), component of various commercially available cleaning products.
Acid-base indicators and pH
Some substances behave differently in the presence of acids or bases. Among them is a group of substances that take on different colors depending on whether the medium in which they are found is acidic or basic. Substances in this group are called acid-base indicators.
There is a numerical scale called pH, with values between 0 and 14, which indicates whether the medium is acidic, basic or neutral.
The pH values are calculated mathematically considering the concentrations of H-and (OH) present in a solution. PH stands for hydrogen potential. The lower the pH value the higher the acidity. In contrast, the higher the pH value, the greater the basicity. It is common, in place of the term basicity, to use the term alkalinity.
The pH scale is for measuring the acid base level. If the level is between 0 and 6 it is acidic. If it is 7 it is neutral. And if it's between 8 and 14, the solution is basic, or alkaline.
Indicators are substances that change color as a function of pH value and can thus serve as a parameter to indicate the pH range of a given sample. For example, phenophthalein is an indicator that, in acidic or neutral medium, is colorless; when in basic medium, it becomes reddish.
Indicators do not report the exact pH value of a solution, they only provide data for assessing whether the medium is acidic, basic or neutral. To know the exact pH value, a special equipment is used, the pH meter (peagameter).
It is possible to mix acids with bases until reaching a neutral pH. This process is called neutralization and consists of a type of chemical reaction.