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الموضوع: Hydrochloric acid HCl

  1. #1
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    افتراضي Hydrochloric acid HCl

    Hydrochloric acid is a solution of hydrogen chloride (HCl) in water, that is a highly corrosive, strongmineral acid with many industrial uses. It is found naturally in gastric acid.
    Historically called muriatic
    acid or spirits of salt, Hydrochloric acid was produced from vitriol (sulfuric acid) and common salt. It first appeared during the Renaissance, and then it was used by chemists like Glauber, Priestley and Davy in their scientific research.
    With major production starting in the
    Industrial Revolution, Hydrochloric acid is used in the chemical industry as a chemical reagent in the large-scale production of vinyl chloride for PVC plastic, and MDI/TDI for polyurethane. It has numerous smaller-scale applications, including household cleaning, production of gelatin and other food additives, descaling, leather processing, and swimming pool maintenance. About 20 million tonnes of Hydrochloric acid are produced annually

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  2. #2
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    افتراضي رد: Hydrochloric acid HCl

    Hydrogen chloride (HCl) is a monoprotic acid, which means it can dissociate (i.e., ionize) only once to give up one H+ ion (a single proton). In aqueous hydrochloric acid, the H+ joins a water molecule to form a hydronium ion, H3O+:[19][20]
    HCl + H2O → H3O+ + Cl−
    The other ion formed is Cl−, the
    chloride ion. Hydrochloric acid can therefore be used to prepare salts called chlorides, such as sodium chloride. Hydrochloric acid is a strong acid, since it is essentially completely dissociated in water.[19][20]
    Monoprotic acids have one
    acid dissociation constant, Ka, which indicates the level of dissociation in water. For a strong acid like HCl, the Ka is large. Theoretical attempts to assign a Ka to HCl have been made.[21] When chloride salts such as NaCl are added to aqueous HCl they have practically no effect on pH, indicating that Cl− is an exceedingly weak conjugate base and that HCl is fully dissociated in aqueous solution. For intermediate to strong solutions of hydrochloric acid, the assumption that H+ molarity (a unit of concentration) equals HCl molarity is excellent, agreeing to four significant digits.[19][20]
    Of the
    six common strong mineral acids in chemistry, hydrochloric acid is the monoprotic acid least likely to undergo an interfering oxidation-reduction reaction. It is one of the least hazardous strong acids to handle; despite its acidity, it consists of the non-reactive and non-toxic chloride ion. Intermediate strength hydrochloric acid solutions are quite stable upon storage, maintaining their concentrations over time. These attributes, plus the fact that it is available as a pure reagent, mean that hydrochloric acid makes an excellent acidifying reagent.
    Hydrochloric acid is the preferred acid in
    titration for determining the amount of bases. Strong acid titrants give more precise results due to a more distinct endpoint. Azeotropic or "constant-boiling" hydrochloric acid (roughly 20.2%) can be used as a primary standard in quantitative analysis, although its exact concentration depends on the atmospheric pressure when it is prepared.[22]
    Hydrochloric acid is frequently used in
    chemical analysis to prepare ("digest") samples for analysis. Concentrated hydrochloric acid dissolves many metals and forms oxidized metal chlorides and hydrogen gas, and it reacts with basic compounds such as calcium carbonate or copper(II) oxide, forming the dissolved chlorides that can be analyzed

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  3. #3
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    افتراضي رد: Hydrochloric acid HCl

    Applications
    Hydrochloric acid is a strong inorganic acid that is used in many industrial processes. The application often determines the required product quality.
    [ Pickling of steel

    One of the most important applications of hydrochloric acid is in the pickling of steel, to remove rust or iron oxide scale from iron or steel before subsequent processing, such as extrusion, rolling, galvanizing, and other techniques. Technical quality HCl at typically 18% concentration is the most commonly used pickling agent for the pickling of carbon steel grades.
    Fe2O3 + Fe + 6 HCl → 3 FeCl2 + 3 H2O
    The
    spent acid has long been re-used as iron(II) chloride (also known as ferrous chloride) solutions, but high heavy-metal levels in the pickling liquor have decreased this practice.
    The steel pickling industry has developed
    hydrochloric acid regeneration processes, such as the spray roaster or the fluidized bed HCl regeneration process, which allow the recovery of HCl from spent pickling liquor. The most common regeneration process is the pyrohydrolysis process, applying the following formula:
    4 FeCl2 + 4 H2O + O2 → 8 HCl+ 2 Fe2O3
    By recuperation of the spent acid, a closed acid loop is established. The
    iron(III) oxide by-product of the regeneration process is valuable, used in a variety of secondary industries.
    Production of organic compounds

    Another major use of hydrochloric acid is in the production of organic compounds, such as vinyl chloride and dichloroethane for PVC. This is often captive use, consuming locally produced hydrochloric acid that never actually reaches the open market. Other organic compounds produced with hydrochloric acid include bisphenol A for polycarbonate, activated carbon, and ascorbic acid, as well as numerous pharmaceutical products.
    2 CH2=CH2 + 4 HCl + O2 → 2 ClCH2CH2Cl + 2 H2O (dichloroethane by
    oxychlorination)
    wood + HCl + heat → activated carbon (
    chemical activation)
    Production of inorganic compounds

    Numerous products can be produced with hydrochloric acid in normal acid-base reactions, resulting in inorganic compounds. These include water treatment chemicals such as iron(III) chloride and polyaluminium chloride (PAC).
    Fe2O3 + 6 HCl → 2 FeCl3 + 3 H2O (iron(III) chloride from
    magnetite)
    Both iron(III) chloride and PAC are used as
    flocculation and coagulation agents in sewage treatment, drinking water production, and paper production.
    Other inorganic compounds produced with hydrochloric acid include road application salt
    calcium chloride, nickel(II) chloride for electroplating, and zinc chloride for the galvanizing industry and battery production.
    CaCO3 + 2 HCl → CaCl2 + CO2 + H2O (calcium chloride from
    limestone)
    pH Control and neutralization

    Hydrochloric acid can be used to regulate the acidity (pH) of solutions.
    OH− + HCl → H2O + Cl−
    In industry demanding purity (food, pharmaceutical, drinking water), high-quality hydrochloric acid is used to control the pH of process water streams. In less-demanding industry, technical quality hydrochloric acid suffices for
    neutralizing waste streams and swimming pool treatment.
    Regeneration of ion exchangers

    High-quality hydrochloric acid is used in the regeneration of ion exchange resins. Cation exchange is widely used to remove ions such as Na+ and Ca2+ from aqueous solutions, producing demineralized water. The acid is used to rinse the cations from the resins.
    Na+ is replaced by H+
    Ca2+ is replaced by 2 H+
    Ion exchangers and demineralized water are used in all chemical industries, drinking water production, and many food industries

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  4. #4
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    افتراضي رد: Hydrochloric acid HCl

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