Acidity hydrogen fluoride

Mercury, chlorine, calcium hypochlorite, iodine, bromine or hydrogen fluoride Acids, metal powders, flammable liquids, chlorates, nitrites, sulphur, finely-divided organics or combustibles Nitric acid, hydrogen peroxide... 

Hydrogen fluoride acid Amide ion (stronger acid, K <==> 1CT4) base... 

Properties Colorless gas. Fp -165C, bp -72C, d (liquid) 1.80. Strong oxidizing agent hydrolyzes to form nitric and hydrogen fluoride acids. 

The company is authorized to engage in foreign trade and exports over US 30 million worth of chemical products each year. It has a joint venture with Bayer to produce polycarbonate with annual capacity of 18 000 tonnes. Major products of the company include liquid caustic soda, solid caustic soda, diaphragm caustic soda, PVC resin, liquid chlorine, muriatic (hydrochloric) acid, chlorinated paraffin, chlorinated rubber, trichloro hydrogen-silicon, sodium hypochlorite, carbon tetrachloride, perchloroethylene, calcium hypochlorite, hydrogen fluoride acid, tetrafluoro-dibromoethane, polytetrafluoroethylene (PTFE) resin, and fluorine refrigerant. 

Consider first two substances which have very similar molecules. He, hydrogen fluoride and HCl. hydrogen chloride the first is a Weak acid in water, the second is a strong acid. To see the reason consider the enthalpy changes involved when each substance in water dissociates to form an acid ... 

The hydrogen fluoride is conveniently produced in situ by the action of concentrated sulphuric acid on calcium fluoride ... 

Silicon tetrafluoride is a colourless gas, b.p. 203 K, the molecule having, like the tetrahalides of carbon, a tetrahedral covalent structure. It reacts with water to form hydrated silica (silica gel, see p. 186) and hexafluorosilicic acid, the latter product being obtained by a reaction between the hydrogen fluoride produced and excess silicon tetrafluoride ... 

The bond dissociation energy of the hydrogen-fluorine bond in HF is so great that the above equilibrium lies to the left and hydrogen fluoride is a weak acid in dilute aqueous solution. In more concentrated solution, however, a second equilibrium reaction becomes important with the fluoride ion forming the complex ion HFJ. The relevant equilibria are ... 

Thus nitric acid behaves as a base in hydrogen fluoride. Hence increases of conductivity when substances dissolve in hydrogen fluoride may be due to acidic or basic behaviour. 

Hydrogen fluoride is the most important compound of fluorine. It is prepared in the laboratory, and on the large scale, by the reaction of calcium fluoride with concentrated sulphuric acid. ... 

The reaction is carried out in a lead retort one suitable for the laboratory can be made from a piece of lead piping, bent like a retort and closed at the shorter end. This is charged with fluorspar and the acid and heated, and the hydrogen fluoride is distilled into a polythene vessel. 

Anhydrous hydrogen fluoride (as distinct from an aqueous solution of hydrofluoric acid) does not attack silica or glass. It reacts with metals to give fluorides, for example with heated iron the anhydrous iron(II) fluoride is formed the same product is obtained by displacement of chlorine from iron(II) chloride ... 

Aqueous hydrogen fluoride is a weak acid (see above) and dissolves silica and silicates to form hexafluorosilicic acid hence glass is etched by the acid, which must be kept in polythene bottles. 

The action of concentrated sulphuric acid liberates hydrogen fluoride, which attacks glass, forming silicon tetrafluoride the latter is hydrolysed to silicic acid by water, which therefore becomes turbid,... 

In dilute aqueous solution hydrogen fluoride is a weak acid but the acid strength increases with the concentration of hydrogen fluoride. 

Another aspect of my early research in Budapest was in nitration chemistry, specifically the preparation of nitronium tetrafluoroborate, a stable nitronium salt. 1 was able to prepare the salt in a simple and efficient way from nitric acid, hydrogen fluoride, and boron trifluoride. 

Perchloric acid (HCIO4 Ho —13.0), fluorosulfuric acid (HSO3F Ho — 15.1), and trifluoromethanesulfonic acid (CF3SO3H Ho —14.1) are considered to be superacids, as is truly anhydrous hydrogen fluoride. Complexing with Lewis acidic metal fluorides of higher valence, such as antimony, tantalum, or niobium pentafluoride, greatly enhances the acidity of all these acids. 

Cations like that present in (iv) exist in solutions of aromatic hydrocarbons in trifluoroacetic acid containing boron trifluoride, and in liquid hydrogen fluoride containing boron trifluoride. Sulphuric acid is able to protonate anthracene at a mero-position to give a similar cation. ... 

Writing the equation in the usual way directs too much attention to the atoms and not enough to the electrons We can remedy that by deleting any spec tator ions and by showing the unshared electron pairs and covalent bonds that are made and broken Both sodium hydroxide and sodium fluoride are com pletely ionized in water therefore Na" which ap pears on both sides of the equation is a spectator ion Hydrogen fluoride is a weak acid and exists as undissociated HF molecules in water... 

The order of reactivity of the hydrogen halides parallels their acidity HI > HBr > HCl >> HF Hydrogen iodide is used infrequently however and the reaction of alco hols with hydrogen fluoride is not a useful method for the preparation of alkyl fluorides Among the various classes of alcohols tertiary alcohols are observed to be the most reactive and primary alcohols the least reactive... 

Hydrogen fluoride Acetic anhydride, 2-aminoethanol, ammonia, arsenic trioxide, chlorosulfonic acid, ethylenediamine, ethyleneimine, fluorine, HgO, oleum, phosphorus trioxide, propylene oxide, sodium, sulfuric acid, vinyl acetate... 

Burns. Skin bums resulting from contact with pure fluorine gas are comparable to thermal bums and differ considerably from those produced by hydrogen fluoride (114). Fluorine bums heal much more rapidly than hydrofluoric acid bums. 

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