Question

Industrial chemists make hydrofluoric acid (which is used in aluminum and uranium processing, to etch glass, and to make CFCs) from the reactions of aqueous calcium fluoride and aqueous sulfuric acid. Write the complete equation for this reaction. (Use the lowest possible coefficients. Include states-of-matter in your answer.)

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Answer 1

The industrial preparation of hydrofluoric acid involves the reaction of CaF2 with conc.H2SO4 at a particular temperature which produces gaseous hydrogen fluoride and solid calcium sulphate is produced as shown below:

CaF2 (aq) + H2SO4 (aq) 2 HF (g) + CaSO4 (s)

(hydrogen fluoride in aqueous state is called hydrofluoric acid)

In hydrofluoric acid processing (to manufacture aluminum and uranium, to etch glass, and to make CFCs),a source of calcium fluoride is fluorite ore(contains 96 wt % CaF2 and 4% SiO2) that is reacted with around 93 wt% aqueous sulphuric acid with an excess of 15% stoichiometric amount. 95% of the ore dissolves in acid and some of HF formed reacts with dissolved silica in the reaction

6HF(g) + SiO2 (aq) H2SiF6(s) + 2H2O(l)

The hydrogen fluoride exiting from the reactor is then dissolved in water to produce hydrofluoric acid.

Thus the reaction can be summarised as:

CaF2 (aq) + H2SO4 (aq) 2 HF (g) + CaSO4 (s)