Anonymous asked in Science & MathematicsChemistry · 1 decade ago

Why can HCl dissolve in water?

Isn't ions soluble in polar solvents while molecules solution in non polar solvent?

So why does HCl, a molecule, dissolve in water, which is a polar solvent to give H+?

9 Answers

  • 1 decade ago
    Favorite Answer

    For thousands of years people have known that vinegar, lemon juice and many other foods taste sour. However, it was not until a few hundred years ago that it was discovered why these things taste sour - because they are all acids. The term acid, in fact, comes from the Latin term acere, which means "sour". While there are many slightly different definitions of acids and bases, in this lesson we will introduce the fundamentals of acid/base chemistry.

    In the seventeenth century, the Irish writer and amateur chemist Robert Boyle first labeled substances as either acids or bases (he called bases alkalies) according to the following characteristics:

    Acids taste sour, are corrosive to metals, change litmus (a dye extracted from lichens) red, and become less acidic when mixed with bases.

    Bases feel slippery, change litmus blue, and become less basic when mixed with acids.

    While Boyle and others tried to explain why acids and bases behave the way they do, the first reasonable definition of acids and bases would not be proposed until 200 years later.

    In the late 1800s, the Swedish scientist Svante Arrhenius proposed that water can dissolve many compounds by separating them into their individual ions. Arrhenius suggested that acids are compounds that contain hydrogen and can dissolve in water to release hydrogen ions into solution. For example, hydrochloric acid (HCl) dissolves in water as follows:

    HCl H2O

    H+(aq) + Cl-(aq)

    Arrhenius defined bases as substances that dissolve in water to release hydroxide ions (OH-) into solution. For example, a typical base according to the Arrhenius definition is sodium hydroxide (NaOH):

    NaOH H2O

    Na+(aq) + OH-(aq)

    The Arrhenius definition of acids and bases explains a number of things. Arrhenius's theory explains why all acids have similar properties to each other (and, conversely, why all bases are similar): because all acids release H+ into solution (and all bases release OH-). The Arrhenius definition also explains Boyle's observation that acids and bases counteract each other. This idea, that a base can make an acid weaker, and vice versa, is called neutralization.

    Neutralization: As you can see from the equations, acids release H+ into solution and bases release OH-. If we were to mix an acid and base together, the H+ ion would combine with the OH- ion to make the molecule H2O, or plain water:

    H+(aq) + OH-(aq) H2O

    The neutralization reaction of an acid with a base will always produce water and a salt, as shown below:

    Acid Base Water Salt

    HCl + NaOH H2O + NaCl

    HBr + KOH H2O + KBr

    Though Arrhenius helped explain the fundamentals of acid/base chemistry, unfortunately his theories have limits. For example, the Arrhenius definition does not explain why some substances, such as common baking soda (NaHCO3), can act like a base even though they do not contain hydroxide ions.

    In 1923, the Danish scientist Johannes Brønsted and the Englishman Thomas Lowry published independent yet similar papers that refined Arrhenius' theory. In Brønsted's words, "... acids and bases are substances that are capable of splitting off or taking up hydrogen ions, respectively." The Brønsted-Lowry definition broadened the Arrhenius concept of acids and bases.

    The Brønsted-Lowry definition of acids is very similar to the Arrhenius definition, any substance that can donate a hydrogen ion is an acid (under the Brønsted definition, acids are often referred to as proton donors because an H+ ion, hydrogen minus its electron, is simply a proton).

    The Brønsted definition of bases is, however, quite different from the Arrhenius definition. The Brønsted base is defined as any substance that can accept a hydrogen ion. In essence, a base is the opposite of an acid. NaOH and KOH, as we saw above, would still be considered bases because they can accept an H+ from an acid to form water. However, the Brønsted-Lowry definition also explains why substances that do not contain OH- can act like bases. Baking soda (NaHCO3), for example, acts like a base by accepting a hydrogen ion from an acid as illustrated below:

    Acid Base Salt

    HCl + NaHCO3 H2CO3 + NaCl


    Under the Brønsted-Lowry definition, both acids and bases are related to the concentration of hydrogen ions present. Acids increase the concentration of hydrogen ions, while bases decrease the concentration of hydrogen ions (by accepting them). The acidity or basicity of something therefore can be measured by its hydrogen ion concentration.

    In 1909, the Danish biochemist Sören Sörensen invented the pH scale for measuring acidity. The pH scale is described by the formula:

    pH = -log [H+] Note: concentration is commonly abbreviated by using square brackets, thus [H+] = hydrogen ion concentration. When measuring pH, [H+] is in units of moles of H+ per liter of solution.

    For example, a solution with [H+] = 1 x 10-7 moles/liter has a pH equal to 7 (a simpler way to think about pH is that it equals the exponent on the H+ concentration, ignoring the minus sign). The pH scale ranges from 0 to 14. Substances with a pH between 0 and less than 7 are acids (pH and [H+] are inversely related - lower pH means higher [H+]). Substances with a pH greater than 7 and up to 14 are bases (higher pH means lower [H+]). Right in the middle, at pH = 7, are neutral substances, for example, pure water. The relationship between [H+] and pH is shown in the table below alongside some common examples of acids and bases in everyday life.

    [H+] pH Example

    Acids 1 X 100 0 HCl

    1 x 10-1 1 Stomach acid

    1 x 10-2 2 Lemon juice

    1 x 10-3 3 Vinegar

    1 x 10-4 4 Soda

    1 x 10-5 5 Rainwater

    1 x 10-6 6 Milk

    Neutral 1 x 10-7 7 Pure water

    Bases 1 x 10-8 8 Egg whites

    1 x 10-9 9 Baking soda

    1 x 10-10 10 Tums® antacid

    1 x 10-11 11 Ammonia

    1 x 10-12 12 Mineral lime - Ca(OH)2

    1 x 10-13 13 Drano®

    1 x 10-14 14 NaOH

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  • 3 years ago

    Is Hcl Soluble In Water

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  • Anonymous
    5 years ago

    This Site Might Help You.


    Why can HCl dissolve in water?

    Isn't ions soluble in polar solvents while molecules solution in non polar solvent?

    So why does HCl, a molecule, dissolve in water, which is a polar solvent to give H+?

    Source(s): hcl dissolve water:
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  • 4 years ago

    For the best answers, search on this site

    It becomes an aqueous solution because HCl is an acid that when placed in water, means that it has dissolved. Dissolved ==>> Aqueous

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  • 4 years ago

    HCL is hydrochloric acid....Water dissolves all acids. Neutralizes them. Makes no sense.

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  • 1 decade ago

    Molecules are not necessarily can not dissolve in water, sugar can dissolve in water.

    HCl can be ionized in water, meaning that H and Cl are separated by polar action of water molecule.. that is why it is soluble.

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  • 1 decade ago

    HCl ionically bonds wd H20 to give it a ball-like surface tension so it copies the properties of H20 whch is a solvent.

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  • 1 decade ago

    all ionic compounds dissolve in water to form an anion and a cation. In the case of acids, the stronger the acid, the more it dissociates and spits off those H's. You get yourself a little cocktail of +H3O and -Cl

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  • 1 decade ago

    The chemical compound hydrochloric acid is the aqueous solution of hydrogen chloride gas (HCl). It is a strong acid, the major component of gastric acid and of wide industrial use. Hydrochloric acid must be handled with appropriate safety precautions because it is a highly corrosive liquid.

    Hydrochloric acid, or muriatic acid by its historical but still occasionally used name, has been an important and frequently used chemical from early history and was discovered by the alchemist Jabir ibn Hayyan around the year 800. It was used throughout the Middle Ages by alchemists in the quest for the philosopher's stone, and later by several European scientists including Glauber, Priestley, and Davy, to help establish modern chemical knowledge.

    From the Industrial Revolution, it became an important industrial chemical for many applications, including the large-scale production of organic compounds, such as vinyl chloride for PVC plastic, and MDI/TDI for polyurethane, and smaller-scale applications, such as production of gelatin and other ingredients in food, and leather processing. About 20 million metric tonnes of HCl gas are produced annually.


    Hydrochloric acid was first discovered around 800 AD by the alchemist Jabir ibn Hayyan (Geber), by mixing common salt with vitriol (sulfuric acid). Jabir discovered many important chemicals, and recorded his findings in over twenty books, which carried his chemical knowledge of hydrochloric acid and other basic chemicals for hundreds of years. Jabir's invention of the gold-dissolving aqua regia, consisting of hydrochloric acid and nitric acid, was of great interest to alchemists searching for the philosopher's stone.

    Jabir ibn Hayyan, medieval manuscript drawingIn the Middle Ages, hydrochloric acid was known to European alchemists as spirit of salt or acidum salis. Gaseous HCl was called marine acid air. The old (pre-systematic) name muriatic acid has the same origin (muriatic means "pertaining to brine or salt"), and this name is still sometimes used. Notable production was recorded by Basilius Valentinus, the alchemist-canon of the Benedictine priory Sankt Peter in Erfurt, Germany in the fifteenth century. In the seventeenth century, Johann Rudolf Glauber from Karlstadt am Main, Germany used sodium chloride salt and sulfuric acid for the preparation of sodium sulfate in the Mannheim process, releasing hydrogen chloride gas. Joseph Priestley of Leeds, England prepared pure hydrogen chloride in 1772, and in 1818 Humphry Davy of Penzance, England proved that the chemical composition included hydrogen and chlorine.

    During the Industrial Revolution in Europe, demand for alkaline substances such as soda ash increased, and the new industrial soda process by Nicolas Leblanc (Issoundun, France) enabled cheap large-scale production. In the Leblanc process, salt is converted to soda ash, using sulfuric acid, limestone, and coal, releasing hydrogen chloride as a by-product. Until the Alkali Act of 1863, excess HCl was vented to the air. After the passage of the act, soda ash producers were obliged to absorb the waste gas in water, producing hydrochloric acid on an industrial scale.

    When early in the twentieth century the Leblanc process was effectively replaced by the Solvay process without the hydrochloric acid by-product, hydrochloric acid was already fully settled as an important chemical in numerous applications. The commercial interest initiated other production methods which are still used today, as described below. Today, most hydrochloric acid is made by absorbing hydrogen chloride from industrial organic compounds production.

    Hydrochloric acid is listed as a Table II precursor under the 1988 Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances because of its use in the production of heroin, cocaine, and methamphetamine.[1]

    [edit] Chemistry

    Acid titrationHydrogen 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+:

    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 fully dissociated in water.

    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.[2] 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.

    Of the seven common strong acids in chemistry, all of them inorganic, 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 produces the less reactive and non-toxic chloride ion. Intermediate strength hydrochloric acid solutions are quite stable, 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 and acid titrant (for determining the amount of an unknown quantity of base in titration). Strong acid titrants are useful because they give more distinct endpoints in a titration, making the titration more precise. Hydrochloric acid is frequently used in chemical analysis and to digest samples for analysis. Concentrated hydrochloric acid will dissolve some metals to form oxidized metal chlorides and hydrogen gas. It will produce metal chlorides from basic compounds such as calcium carbonate or copper(II) oxide. It is also used as a simple acid catalyst for some chemical reactions.

    [edit] Physical properties

    The physical properties of hydrochloric acid, such as boiling and melting points, density, and pH depend on the concentration or molarity of HCl in the acid solution. They can range from those of water at 0% HCl to values for fuming hydrochloric acid at over 40% HCl.

    Conc. (w/w)

    c : kg HCl/kg Conc. (w/v)

    c : kg HCl/m3 Conc.



    ρ : kg/l Molarity

    M pH


    η : mPa·s Specific


    s : kJ/(kg·K) Vapor


    PHCl : Pa Boiling


    b.p. Melting



    10% 104.80 6.6 1.048 2.87 M -0.5 1.16 3.47 0.527 103 °C -18 °C

    20% 219.60 13 1.098 6.02 M -0.8 1.37 2.99 27.3 108 °C -59 °C

    30% 344.70 19 1.149 9.45 M -1.0 1.70 2.60 1,410 90 °C -52 °C

    32% 370.88 20 1.159 10.17 M -1.0 1.80 2.55 3,130 84 °C -43 °C

    34% 397.46 21 1.169 10.90 M -1.0 1.90 2.50 6,733 71 °C -36 °C

    36% 424.44 22 1.179 11.64 M -1.1 1.99 2.46 14,100 61 °C -30 °C

    38% 451.82 23 1.189 12.39 M -1.1 2.10 2.43 28,000 48 °C -26 °C

    The reference temperature and pressure for the above table are 20 °C and 1 atmosphere (101 kPa).

    Hydrochloric acid as the binary (two-component) mixture of HCl and H2O has a constant-boiling azeotrope at 20.2% HCl and 108.6 °C (227 °F). There are four constant-crystallization eutectic points for hydrochloric acid, between the crystal form of HCl·H2O (68% HCl), HCl·2H2O (51% HCl), HCl·3H2O (41% HCl), HCl·6H2O (25% HCl), and ice (0% HCl). There is also a metastable eutectic point at 24.8% between ice and the HCl·3H2O crystallization

    [edit] Production

    Main article: hydrogen chloride

    Hydrochloric acid is prepared by dissolving hydrogen chloride in water. Hydrogen chloride can be generated in many ways, and thus several different precursors to hydrochloric acid exist. The large scale production of hydrochloric acid is almost always integrated with other industrial scale chemicals production.

    [edit] Industrial market

    Hydrochloric acid is produced in solutions up to 38% HCl (concentrated grade). Higher concentrations up to just over 40% are chemically possible, but the evaporation rate is then so high that storage and handling need extra precautions, such as pressure and low temperature. Bulk industrial-grade is therefore 30% to 34%, optimized for effective transport and limited product loss by HCl vapors. Solutions for household purposes, mostly cleaning, are typically 10% to 12%, with strong recommendations to dilute before use.

    Major producers worldwide include Dow Chemical at 2 million metric tonnes annually (2 Mt/year), calculated as HCl gas, and FMC, Georgia Gulf Corporation, Tosoh Corporation, Akzo Nobel, and Tessenderlo at 0.5 to 1.5 Mt/year each. Total world production, for comparison purposes expressed as HCl, is estimated at 20 Mt/year, with 3 Mt/year from direct synthesis, and the rest as secondary product from organic and similar syntheses. By far, most of all hydrochloric acid is consumed captively by the producer. The open world market size is estimated at 5 Mt/year.

    [edit] Applications

    Hydrochloric acid is a common laboratory reagent.Hydrochloric acid is a strong inorganic acid that is used in many industrial processes. The application often determines the required product quality.

    [edit] Regeneration of ion exchangers

    An important application of high-quality hydrochloric acid is 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.

    Na+ is replaced by H3O+

    Ca2+ is replaced by 2 H3O+

    Ion exchangers and demineralized water are used in all chemical industries, drinking water production, and many food industries.

    [edit] pH Control and neutralization

    A very common application of hydrochloric acid is to regulate the basicity (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.

    [edit] Pickling of steel

    Pickling is an essential step in metal surface treatment, 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 ferrous chloride solutions, but high heavy-metal levels in the pickling liquor has decreased this practice.

    In recent years, the steel pickling industry has however 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 ferric oxide by product of the regeneration process is a valuable by-product, used in a variety of secondary industries.

    HCl is not a common pickling agent for stainless steel grades.

    [edit] 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

    Both iron(III) chloride and PAC are used as flocculation and coagulation agents in wastewater 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.

    [edit] Production of organic compounds

    The largest hydrochloric acid consumption is in the production of organic compounds such as vinyl chloride for PVC, and MDI and TDI for polyurethane. 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.

    [edit] Other applications

    Hydrochloric acid is a fundamental chemical, and as such it is used for a large number of small-scale applications, such as leather processing, household cleaning, and building construction. In addition, a way of stimulating oil production is by injecting hydrochloric acid into the rock formation of an oil well, dissolving a portion of the rock, and creating a large-pore structure. Oil-well acidizing is a common process in the North Sea oil production industry.

    Many chemical reactions involving hydrochloric acid are applied in the production of food, food ingredients, and food additives. Typical products include aspartame, fructose, citric acid, lysine, hydrolyzed (vegetable) protein as food enhancer, and in gelatin production. Food-grade (extra-pure) hydrochloric acid can be applied when needed for the final product.

    [edit] Presence in living organisms

    [edit] Physiology and pathology

    Hydrochloric acid constitutes the majority of gastric acid, the human digestive fluid. In a complex process and at a large energetic burden, it is secreted by parietal cells (also known as oxyntic cells). These cells contain an extensive secretory network (called canaliculi) from which the HCl is secreted into the lumen of the stomach. They are part of the fundic glands (also known as oxyntic glands) in the stomach.

    Safety mechanisms that prevent the damage of the epithelium of digestive tract by hydrochloric acid are the following:

    Negative regulators of its release

    A thick mucus layer covering the epithelium

    Sodium bicarbonate secreted by gastric epithelial cells and pancreas

    The structure of epithelium (tight junctions)

    Adequate blood supply

    Prostaglandins (many different effects: they stimulate mucus and bicarbonate secretion, maintain epithelial barrier integrity, enable adequate blood supply, stimulate the healing of the damaged mucous membrane)

    When, due to different reasons, these mechanisms fail, heartburn or peptic ulcers can develop. Drugs called proton pump inhibitors prevent the body from making excess acid in the stomach, while antacids neutralize existing acid.

    In some instances, the stomach does not produce enough hydrochloric acid. These pathologic states are denoted by the terms hypochlorhydria and achlorhydria. Potentially they can lead to gastroenteritis.

    [edit] Chemical weapons

    Phosgene (COCl2) was a common chemical warfare agent used in World War I. The main effect of phosgene results from the dissolution of the gas in the mucous membranes deep in the lung, where it is converted by hydrolysis into carbonic acid and the corrosive hydrochloric acid. The latter disrupts the alveolar-capillary membranes so that the lung becomes filled with fluid (pulmonary edema).

    Hydrochloric acid is also partly responsible for the harmful or blistering effects of mustard gas. In the presence of water, such as on the moist surface of the eyes or lungs, mustard gas breaks down forming hydrochloric acid.

    [edit] Safety

    Dangerous goods labels

    Hydrochloric acid in high concentrations forms acidic mists. Both the mist and the solution have a corrosive effect on human tissue, potentially damaging respiratory organs, eyes, skin and intestines. Upon mixing hydrochloric acid with common oxidizing chemicals, such as bleach (NaClO) or permanganate (KMnO4), the toxic gas chlorine is produced. To minimize the risks while working with hydrochloric acid, appropriate precautions should be taken, including wearing rubber or PVC gloves, protective eye goggles, and chemical resistant clothing.

    The hazards of solutions of hydrochloric acid depend on the concentration. The following table lists the EU classification of hydrochloric acid solutions:


    by weight Classification R-Phrases

    10%–25% Irritant (Xi) R36/37/38

    >25% Corrosive (C) R34 R37

    The Environmental Protection Agency rates and regulates hydrochloric acid as a toxin.[3]

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