What are the strongest bases and acids found in nature?
You may be surprised at the range of acid and base strengths we encounter, from mineral acids to alkaline earths. Read the explanation.
One naturally ocurring strong acid is hydrochloric acid in the digestive juice of our own stomachs. Less obvious, but essential in releasing nutrients to the soil, are very dilute acids present in rainwater. Nitric acid can be produced in electrical storms when nitrogen, oxygen, and water vapor are combined through the action of lightning. Sulfuric acid may be formed if sulfur-bearing compounds are present from volcanoes or, unfortunately, from air pollution. Sulfuric acid is also formed on the ground by oxidation of sulfide minerals such as pyrites.
Naturally occurring water contains dissolved carbon dioxide and bicarbonates, both of which react with strong bases. So the strongest bases in nature are based on compounds with limited solubility in water. Lime (calcium oxide) can be formed by volcanic heat calcining limestone, and this may react with water to make the calcium hydroxide mineral portlandite.
The corresponding magnesium minerals periclase (magnesium oxide, or magnesia) and brucite (magnesium hydroxide) are less strongly basic but appreciably more common. Although magnesium hydroxide is often called a weak base, it is in fact relatively strong compared with most metal hydroxides. Lime and magnesia are the quintessential "alkaline earths" for which the Group 2 metals are named.