<Dl> <Dd> 3 HF ⇌ H F + HF − </Dd> </Dl> <Dd> 3 HF ⇌ H F + HF − </Dd> <P> which forms an extremely acidic solution (H = − 11). </P> <P> The acidity of anhydrous HF can be increased even further by the addition of Lewis acids such as SbF, which can reduce H to − 21 . </P>

Hydrogen fluoride gas reacts with water to form an acidic solution