Acids are molecules or ions that can lose protons (hydrogen ions (H + ions) or instead be able to bond covalently with an electron pair (a Lewis acid). Acid is derived from the Latin word acidus / acēre meaning sour.
The first group of acids are proton or Bronsted-Lori. Forming blue solutions with a sour taste, they can turn blue measuring paper red and react with certain bases and metals (such as calcium) to form salt. The aqueous solution of an acid has a pH of less than 7.
The second group of acids are Lewis acids, which form a covalent bond with a pair of electrons. For example, boron trifluoride (BF3), whose boron atom has an empty orbit, can form a covalent bond by sharing a single electron pair on an atom at a base, such as nitrogen atoms in ammonia (NH3).
Acids, in a conversational sense, can be pure solutions or substances and are derived from acids in the true sense that can be solid, liquid, or gas. Strong acids and some weakly concentrated acids are corrosive, but there are exceptions such as carboran and boric acid.
The strength of an acid refers to its ability or tendency to lose protons. A strong acid that is completely soluble in water. In other words, one mole of a strong HA acid dissolves in water, leaving one molar H and one mole A, and none of the protein has HA protein. In contrast, a weak acid is only partially separated, and in equilibrium both the acid and the conjugate base remain in solution.
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