Hydrofluoric acid equilibria with

Anhydrous hydrogen fluoride and hydrofluoric acid react with substances containing silica and silicon oxide to form silicon tetrafluoridc and fluorosilic acid. SiF, a colorless gas at ambient temperature, is liighly toxic. An equilibrium mixture of SiF in the presence of moisture also contains hydrogen fluoride and hydrofluoric acid. 

A weak acid is one that is only partially dissociated in water. Only a small fraction of the weak acid molecules transfer a proton to water, and the solution therefore contains mainly undissociated HA molecules along with small amounts of H30+ and the conjugate base A-. Typical weak acids are nitrous acid (HNO2), hydrofluoric acid (HF), and acetic acid (CH3C02H). In the case of very weak acids such as NH3, OH-, and H2, the acid has practically no tendency to transfer a proton to water, and the acid-dissociation equilibrium lies essentially 100% to the left. It follows from this definition that very weak acids have strong conjugate... 

PbF2 (c). Guntz1 found 2.2 for the heat of reaction of aqueous lead nitrate with aqueous hydrofluoric acid. This gives for PbF2 (c), Qf=159.5. From equilibrium data, Jellinek and Rudat1 calculated Qf=156. 

The acid dissociation constant is 6.7 X 10 . (The fluoride ion from the sodium fluoride shifts this equilibrium to the left it does not react directly with the hydrofluoric acid.) Start by assuming that no hydronium ion is present ... 

Hydrofluoric acid (bp, 19.5°C Tc, 188°C Pc, 64 atm), nitrogen dioxide (bp, 21°C Tc, 158.2°C Pc, 100 atm in equilibrium with N2O4), sulfuric acid (decomposition at 280°C), and polyphosphoric acid are candidates for solvents in solvothermal reactions, and the reactions of these solvents will produce a variety of products that cannot be prepared by any other methods. For example, Bialowons et al. reported that solvothermal treatment of (02)2Ti7F3o in anhydrous HF at 300°C yielded single crystals of TiF4. Solvothermal reactions in these solvents may produce fruitful results and a new field seems to be awaiting many researchers. 

When a base is added to the hydrofluoric acid/fluoride ion buffer system, the added OH ions react with H+ ions to form water. This decreases the concentration of hydrogen ions and the equilibrium shifts to the right to replace the H ions. 

The addition takes place according to Markownikoff s rule. The addition of carbo lic acida to the double bonds of isobutylene and trimethyl-ethylene gives tertiary esters. A true equilibrium independent of sulfuric acid concentrations is established in the exothermic reaction. The addition does not go well with ethylene, but goes well with many of the higher alkenes, particularly with some of the terpenes. To avoid the polymerizing effects of sulfuric acid, various other catalysts, such as sulfonic acids, triethylamine, hydrofluoric acid, boron trifluoride, and cuprous chloride have been used. The addition may take place at room temperature or higher and is aided by pressure. The vapors of the acid and hydrocarbon may be passed over catalysts, such as activated carbon, heteropoly acids, or metal phosphates. ... 

Write chemical equations and equilibrium expressions for the reactions of each of the following weak acids with water (a) acetic acid, CH3COOH, (b) propanoic acid, C2H5COOH, (c) hydrofluoric acid, HE, (d) hypochlorous acid, HCIO, (e) carbonic acid, H2CO3... 

The samples were placed in small Alsint crucibles which were inside a larger crucible. In this way, the same experimental conditions such as temperature and atmosphere could be guaranteed for the different salt/metal (CuCl2/Hf) ratios. The crucible was placed in a gas-tight chamber furnace. The samples were heated to 850 °C and maintained at equilibrium temperature for 4h. After cooling to room temperature, the metal phase was separated from the salt and cut into smaller pieces of about 1 -3 g for analysis. These pieces were dissolved in a combination of 10 ml hydrofluoric acid and 20 ml nitric acid, made up to 100 ml with demineralised water. The leachate was filtered and then analysed with ICP-OES using a PerkinElmer Optima 5300DV. 

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