Equations Hydrofluoric acid

Hydrated amorphous silica dissolves more rapidly than does the anhydrous amorphous silica. The solubility in neutral dilute aqueous salt solutions is only slighdy less than in pure water. The presence of dissolved salts increases the rate of dissolution in neutral solution. Trace amounts of impurities, especially aluminum or iron (24,25), cause a decrease in solubility. Acid cleaning of impure silica to remove metal ions increases its solubility. The dissolution of amorphous silica is significantly accelerated by hydroxyl ion at high pH values and by hydrofluoric acid at low pH values (1). Dissolution follows first-order kinetic behavior and is dependent on the equilibria shown in equations 2 and 3. Below a pH value of 9, the solubility of amorphous silica is independent of pH. Above pH 9, the solubility of amorphous silica increases because of increased ionization of monosilicic acid. 

Aqueous hydrofluoric acid dissolved in acetonitrile is a good catalyst for intramolecular Diels-Alder reactions [9] This reagent promotes highly stereoselective cyclizations of different triene esters (equation 8) The use of other acids, such as hydrochloric, acetic, and trifluoroacetic acid, results in complete polymerization of the starting trienes [9] (equation 8)... 

Attack by alkali solution, hydrofluoric acid and phosphoric acid A common feature of these corrosive agents is their ability to disrupt the network. Equation 18.1 shows the nature of the attack in alkaline solution where unlimited numbers of OH ions are available. This process is not encumbered by the formation of porous layers and the amount of leached matter is linearly dependent on time. Consequently the extent of attack by strong alkali is usually far greater than either acid or water attack. 

HF appears in this equation because hydrofluoric acid is weak, containing many more HF molecules than H+ ions. Similarly, for the reaction of these two acids with a solution of sodium carbonate ... 

Write a balanced equation for the reaction of hydrofluoric acid with Si02. What volume of 2.0 M HF is required to react with one gram of silicon dioxide ... 

C) for cast iron and up to 140 °F for marstenitic SS (60 °C). It is widely used where silicates are present with the iron oxides. Typically, 5 to 7.5% HC1 is employed. The ammonium bifluoride normally is present at 0.5%, but it may be increased to a maximum of 1.5% for a boiler that has not been cleaned for many years. The presence of hydrofluoric acid (HF), which is formed by the reaction of ammonium bifluoride with HC1 (see equation), tends to increase the rate of iron oxide dissolution and reduce the corrosion rate of exposed steel, when compared to using HC1 alone. This is due to the stability of the hexafluoroferric ion (FeFg3 ), which prevents the ferric ion from corroding exposed steel. 

H.13 Hydrofluoric acid is used to etch grooves in glass because it reacts with the silica, Si02(s), in glass. The products of the reaction are aqueous silicon tetrafluoride and water. Write a balanced equation for the reaction. 

Write balanced chemical equations for the following reactions (a) Hydrogen fluoride is produced by the reaction of hydrochloric acid and sodium fluoride. (b) Hydrochloric acid combines with sodium fluoride to yield hydrogen fluoride, (c) Sodium fluoride reacts with hydrochloric acid to give hydrofluoric acid. 

All the separated ions should have (aq) after their formulas, as should the hydrofluoric acid. Water is a liquid, and carbon dioxide is a gas. The insoluble ionic materials, including those that are not strong bases, are solids. When we add this information, we have the ionic equations ... 

Properties of aqueous hydrofluoric acid. Top row indicates unit and equation or reference used for calculation. Bold values are certified by experimental data. 

In the case of the aromatic substances, the aromatic cation and the fluoride anion are present in anhydrous hydrofluoric acid. If we use equation (5), then the known laws for weak electrolytes may be used for this formation equilibrium. If the degree of formation of the aromatic... 

Etching of Glass with Hydrofluoric Acid. Cover a glass plate with a layer of paraffin. To do this, lower it into paraffin melted in a porcelain bowl and immediately extract it. Make an inscription with a penknife on the paraffin-coated surface so as to uncover the surface of the glass. Make a small paraffin barrier at the edges of the inscription. Pour a 10% hydrofluoric acid solution onto the paraffin-coated plate and let it stand in a fume cupboard. After one or two hours, wash the solution off the plate and remove the paraffin. What happened to the glass Write the equations of the reactions. 

Preparation of Silicic Acid Anhydride. Dissolve a small amount of potassium silicate in a minimum amount of water, filter the solution if necessary, and add a 37 % hydrochloric acid solution up to a strongly acidic reaction. Transfer the solution into a porcelain bowl and evaporate it until dry in a sand bath. Wash the dry residue with warm water until the chloride ions are removed, then roast it and see how it reacts with solutions of an alkali and hydrofluoric acid in a lead bowl in a jum cupboard ). Write the equations of the reactions. What is obtained when silicic acid anhydride is melted with alkalies ... 

Acetyl fluoride (A) reacts with water (B) to form acetic acid (C) and hydrofluoric acid (D). The reaction is carried out in acetone (an inert solvent) so that the concentrations can be kept low and the reaction under control. The equation is... 

Alkyl silyl ethers are cleaved by a variety of reagents Whether the silicon-oxygen or the carbon-oxygen bond is cleaved depends on the nature of the reagent used Treatment of alkoxysilanes with electrophilic reagents like antimony tn-fluonde, 40% hydrofluoric acid, or a boron tnfluonde-ether complex results in the cleavage of the silicon-oxygen bond to form mono-, di-, and tnfluorosiloxanes or silanes [19, 20, 21] (equations 18-20)... 

Stability toward reduction makes hydrogen fluoride a good medium for different hydrogenation processes [1, 2] It is a useful solvent for the hydrogenation of benzene in the presence of Lewis acids [1] Anhydrous hydrofluoric acid has pronounced catalytic effect on the hydrogenations of various aromatic compounds, aliphatic ketones, acids, esters, and anhydrides in the presence of platinum dioxide [2] (equations 1-3)... 

Xenon hexafluoride reacts with water to produce xenon trioxide and hydrofluoric acid. Write the chemical equation for the reaction. 

The balanced equation below describes the process for etching glass (Si02) by treating it with the highly corrosive hydrofluoric acid (HF). 

Mix 0.5 gram of the precipitated silica with 1 gram of powdered calcium fluoride. Place the mixture in a test tube, moisten it with 36 N H2S04, and warm it gently under the hood. Dip a stirring rod in water and lower it, with a drop adhering, into the gas in the test tube. Note the precipitate that forms in the drop of water. Write equations for all the reactions, and state what rather unusual properties are shown by this experiment to be possessed by hydrofluoric acid and by silicon tetrafluoride. 

However, when [(trimethylsilyl)ethynyl]phenyliodonium tetrafluoroborate is treated with 46% aqueous hydrofluoric acid, protodesilylation occurs, and ethynyl(phenyl)iodonium tetrafluoroborate is obtained in high yield (equation 27)27. 

Hydrohalides dissolve easily in water to form hydrohalic acids and undergo virtually complete ionic dissociation (equation 84). All the hydrohalic acids, except HF, are very strong acids. Although AHF is one of the most acidic liquids, as measured by its Hammett function, hydrofluoric acid is a weak acid. 

Boron forms strong bonds to fluorine (644kJmol ), usually combining with three or four fluorides in its compounds or salts. Several binary fluorides of boron are known including boron trifluoride, BF3, a stable gas of great industrial importance as a Lewis acid. Boron trifluoride is synthesized industrially by reaction of hydrofluoric acid with borates or boric oxides (equation 42). ... 

SF4 is rapidly hydrolyzed by water to give thionyl fluoride and hydrofluoric acid and so great care must be exercised when using it as a reagent. It can be used (Figure 39) as a powerful fluorinating agent (equations 49 and 50). 

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