Rubidium hydrogen sulfate, sometimes referred to as rubidium bisulfate, is the half neutralized rubidium salt of sulfuric acid. It has the formula RbHSO<sub>4</sub>.
It is a hygroscopic compound.
Its crystals are isomorphs with ammonium hydrogen sulfate crystals.
Its enthalpy of solution is 15.62 kJ/mol.
After warming up it decomposes to rubidium disulfate and water:
It may be synthesised with water and a stoichiometric amount of rubidium disulfate. Reaction takes place where there is no humidity:
There is another method of creation. It is similar to the synthesis of sodium sulfate and potassium sulfate. This reaction requires rubidium chloride and a little bit of warm sulfuric acid. Some hydrogen chloride is also produced during the reaction.
Like potassium and caesium, rubidium has another hydrogen sulfate compound as well: Rb<sub>3</sub>H(SO<sub>4</sub>)<sub>2</sub>.