Common Chemical Formulas
A curated set of the compounds that appear in nearly every chemistry course — each with an original explanation, molar mass breakdown, uses and the questions students actually ask. This is a hand-written collection, not an auto-generated database.
How to read a chemical formula
A chemical formula lists the elements in a compound and how many atoms of each it contains. The subscript number after a symbol counts the atoms of that element, so H₂O means two hydrogen atoms and one oxygen atom, while CO₂ means one carbon and two oxygen. A number in front of a formula multiplies the whole unit, and parentheses group atoms that repeat — Ca(OH)₂ contains one calcium, two oxygen and two hydrogen atoms. Reading formulas confidently is the first step toward calculating molar mass and balancing equations.
Why these compounds
This is a hand-picked set of the compounds that appear in nearly every chemistry course, from water, salt and carbon dioxide to glucose, ammonia and sulfuric acid. Each has its own page with an original explanation, a molar-mass breakdown, common uses and the questions students most often ask. To work out the mass of any formula yourself, use the molar mass calculator.