(3) Hydrogen fluoride is a chemical compound with the chemical formula HF. This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock in the preparation of many important compounds including pharmaceuticals and polymers (e.g. Teflon). HF is widely used in the petrochemical industry as a component of superacids. Hydrogen fluoride boils near room temperature, much higher than other hydrogen halides. HF bond has the highest hydrogen bond strength. The most reliable value is 38.6 kcal/mol or 161.5 kJ/mol. The other bonds are relatively low in strength, for example: O—H...: N (7 kJ/mol) O—H...: O (5 kJ/mol) N—H...: N (3 kJ/mol) N—H...: O (2 kJ/mol)