What is an alkali?
Alkali is the alternative name for base. Arrhenius theory of acids and bases can define the pH scale in the best possible manner. According to the Arrhenius theory, an alkali is a substance that produces free OH– in its aqueous solution, while an acid is a substance that produces free H+ ions in the solution.
The pH scale ranges from 1 to 10. As we move from pH 1 to 10, the acidity of the substance decreases, while the basicity increases accordingly. At pH = 7, the system attains neutrality. So, a substance with pH = 7, is neither acidic nor alkaline.
Water is the neutral substance with pH = 7. Beyond pH = 7, substances will be termed as basic and the basicity keeps on increasing till pH = 14. NaOH is the strongest base at pH = 13; lime water is a moderately strong base at pH = 10; borax is a weak alkali at pH = 9; baking soda is the weakest alkali at pH = 8.0
Alkali have a slippery feel with a bitter taste.
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkali earth metal element. Alkalis are best known for being bases (compounds with pH greater than 7) that dissolve in water. All alkalis have a pH greater than seven and hence can be detected with litmus paper (litmus will turn blue on contact with an alkali). Most alkalis have a pH of 10 or greater. This means that they will turn phenolphthalein from colorless to pink. Caustic (causing chemical burns). Alkaline solutions are slippery or soapy to the touch (due to the caustic reaction dissolving the surface of the skin and fingerprint). Alkalis normally form aqueous solutions (although some like barium carbonate are only soluble when reacting with an acidic aqueous solution).
An alkali is a caustic material. Alkalies have a corrosive or irritating effect on living tissue. Like acids, alkalies burn skin. But alkalies are sneakier than acids. Alkalies damage skin slowly. An alkali such as wet Portland cement can stay on your skin for several hours before you feel the chemical burn. Acidity and alkalinity are measured on a pH scale.
