examples of bases and their uses
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In chemistry, the term base metal is used informally to refer to a metal that oxidizes or corrodes relatively easily, and reacts variably with diluted hydrochloric acid (HCl) to form hydrogen. Examples include iron, nickel, lead and zinc. Copper is considered a base metal as it oxidizes relatively easily, although it does not react with HCl.
Base is used in the sense of low-born, in opposition to noble or precious metal. In alchemy, a base metal was a common and inexpensive metal, as opposed to precious metals, mainly gold and silver. A long-time goal of the alchemists was the transmutation of base metal into precious metal.
In mining and economics, base metals refers to industrial non-ferrous metals excluding precious metals. These include copper, lead, nickel and zinc. The U.S. Customs and Border Protection is more inclusive in its definition. It includes, in addition to the four above, iron and steel, aluminium, tin, tungsten, molybdenum, tantalum, magnesium, cobalt, bismuth, cadmium, titanium, zirconium, antimony, manganese, beryllium, chromium, germanium, vanadium, gallium, hafnium, indium, niobium, rhenium and thallium.
Bases are considered the chemical opposite of acids because of their ability to neutralize acids. In 1887 the Swedish physicist and chemist Svante Arrhenius defined a base as the chemical substance that produces hydroxide ions (OHâˆ’) and cations. A typical base, according to the Arrhenius definition, is sodium hydroxide (NaOH). The neutralization of an acid with a base to yield salt and water may be represented as HCl (aq ) + KOH (aq ) â‡† H2O (l ) + KCl (aq ) Â Â Â Â Â (1) A major problem with Arrhenius's definition of bases is that several chemical compounds, such as NaHCO3, Na2CO3, Na3PO4, which produce basic solutions when dissolved in water, do not contain hydroxide ions. The BrÃ¸nsted-Lowry theory, which was proposed independently by Danish chemist Johannes BrÃ¸nsted and English chemist Thomas Lowry in 1923, states that a base accepts hydrogen ions and an acid donates hydrogen ions. This theory not only includes all bases containing hydroxide ions, but also covers any chemical species that are able to accept hydrogen ions in aqueous solution . For example, when sodium carbonate is dissolved in solution, the carbonate ion accepts a hydrogen ion from water to form the bicarbonate ion and hydroxide ion. (2) The BrÃ¸nsted-Lowry theory includes water as a reactant and considers its acidity or basicity. In reaction (2) a new acid and base are formed, which are called the conjugate acid and conjugate base, respectively. The strength of a base is determined by the extent of its ionization in aqueous solution. Strong bases, such as NaOH, are 100 percent ionized in aqueous solution and weak bases, such as ammonia, are only partially ionized in aqueous solution. (3) The partial ionization is a dynamic equilibrium , as indicated by the double arrow in equation (3). The strength of acids and bases also determines the strength of their conjugate bases and conjugate acids, respectively. Weak acids and bases have strong conjugate bases and acids. For example, when ammonium chloride is dissolved in water, it gives an acidic solution because ammonium ion is a strong conjugate acid of the weak base ammonia, but chloride ion is a weak conjugate base of the strong acid hydrochloric acid. NH4+ (aq ) + H2O (l ) â†’ NH3 (aq ) + H3O+ (aq ) Â Â Â Â Â (4) The carbonate ion in equation (2) yields a basic solution because it is the strong conjugate base of the weak acid HCO3âˆ’. When NaHCO3 is dissolved in water, it gives a basic solution, even though a hydrogen ion is available. Predicting this requires one to consider the strength of carbonic acid, H2CO3, which is a very weak acid. H2CO3 (aq ) + H2O (l ) â‡† HCO3âˆ’ (aq ) + H3O+ (aq ) Â Â Â Â Â (5) However, HCO3âˆ’ will act as an acid if a strong base is added. HCO3âˆ’ (aq ) + OHâˆ’ (aq ) â†’ H2O (l ) + CO32âˆ’ (aq ) Â Â Â Â Â (6) This ability to act as a base or an acid is called amphoterism. Any anions of polyprotic acids, such as HCO3âˆ’, H2PO4âˆ’, and HPO42âˆ’, which contain replaceable hydrogen ions, are amphoteric. Some hydroxides, such as Al(OH)3 and Zn(OH)2, are also amphoteric, reacting with a base or acid, as illustrated by the following equations: Al(OH)3 (s ) + OHâˆ’ (aq ) â†’ Al(OH)4âˆ’ (aq ) Â Â Â Â Â (7) Al(OH)3 (s ) + 3 H3O+ (aq ) â†’ Al3+ (aq ) + 6 H2O (l ) Â Â Â Â Â (8) Equations (7) and (8) can also be explained by American chemist Gilbert Lewis's acid-base theory. A Lewis acid is a substance that can accept a pair of electrons to form a new bond, and a Lewis base is a substance that can donate a pair of electrons to form a new bond. (9) All Arrhenius and BrÃ¸nsted-Lowry bases are also Lewis bases. All metal cations are potential Lewis acids. Complexes of metal ions with water, ammonia, and hydroxide ion are examples of Lewis acid-base reactions. For example, [Al(H2O)6]3+ may be regarded as a combination of the Lewis acid, Al3+, with six electron pairs from six H2O molecules. Buffer solutions contain a base and an acid that can react with an added acid or base, respectively, and they maintain a pH very close to the original value. Buffers usually consist of approximately equal quantities of a weak acid and its conjugate base, or a weak base and its conjugate acid. For example, one of the buffers used to keep the pH of the blood near 7.45 is the H2PO4âˆ’/HPO42âˆ’ acid/conjugate base system. Small amounts of an acid or base react with one of the components of the buffer mixture to produce the other component as follows: H2PO4âˆ’ (aq ) + OHâˆ’ (aq ) â†’ H2O (l ) + HPO42âˆ’ (aq ) Â Â Â Â Â (10) HPO42âˆ’ (aq ) + H3O+ (aq ) â†’ H2O (l ) + H2PO4âˆ’ (aq ) Â Â Â Â Â (11) see also Acid-Base Chemistry; Arrhenius, Svante; BrÃ˜nsted, Johannes Nicolaus; Chemical Reactions; Lewis, Gilbert N.; Solution Chemistry. Melvin D. Joesten Joesten, Melvin D., and Wood, James L. (1996). The World of Chemistry, 2nd edition. Fort Worth, TX: Saunders College. Moore, John W.; Stanitski, Conrad L.; Wood, James L.; Kotz, John C.; and Joesten, Melvin D. (1998). The Chemical World, 2nd edition. Philadelphia: Saunders. Carpi, Anthony. "Acids and Bases: An Introduction." Visionlearning. Available from
acids and bases two related classes of chemicals; the members of each class have a number of common properties when dissolved in a solvent, usually water. Properties Acids in water solutions exhibit the following common properties: they taste sour; turn litmus paper red; and react with certain metals, such as zinc, to yield hydrogen gas. Bases in water solutions exhibit these common properties: they taste bitter; turn litmus paper blue; and feel slippery. When a water solution of acid is mixed with a water solution of base, water and a salt are formed; this process, called neutralization , is complete only if the resulting solution has neither acidic nor basic properties. Classification Acids and bases can be classified as organic or inorganic. Some of the more common organic acids are: citric acid , carbonic acid , hydrogen cyanide , salicylic acid, lactic acid , and tartaric acid . Some examples of organic bases are: pyridine and ethylamine. Some of the common inorganic acids are: hydrogen sulfide , phosphoric acid , hydrogen chloride , and sulfuric acid . Some common inorganic bases are: sodium hydroxide , sodium carbonate , sodium bicarbonate , calcium hydroxide , and calcium carbonate . Acids, such as hydrochloric acid, and bases, such as potassium hydroxide, that have a great tendency to dissociate in water are completely ionized in solution; they are called strong acids or strong bases. Acids, such as acetic acid, and bases, such as ammonia, that are reluctant to dissociate in water are only partially ionized in solution; they are called weak acids or weak bases. Strong acids in solution produce a high concentration of hydrogen ions, and strong bases in solution produce a high concentration of hydroxide ions and a correspondingly low concentration of hydrogen ions. The hydrogen ion concentration is often expressed in terms of its negative logarithm, or p H (see separate article). Strong acids and strong bases make very good electrolytes (see electrolysis ), i.e., their solutions readily conduct electricity. Weak acids and weak bases make poor electrolytes. See buffer ; catalyst ; indicators, acid-base ; titration . Acid-Base Theories There are three theories that identify a singular characteristic which defines an acid and a base: the Arrhenius theory, for which the Swedish chemist Svante Arrhenius was awarded the 1903 Nobel Prize in chemistry; the BrÃ¶nsted-Lowry, or proton donor, theory, advanced in 1923; and the Lewis, or electron-pair, theory, which was also presented in 1923. Each of the three theories has its own advantages and disadvantages; each is useful under certain conditions. The Arrhenius Theory When an acid or base dissolves in water, a certain percentage of the acid or base particles will break up, or dissociate (see dissociation ), into oppositely charged ions. The Arrhenius theory defines an acid as a compound that can dissociate in water to yield hydrogen ions, H + , and a base as a compound that can dissociate in water to yield hydroxide ions, OH - Â . For example, hydrochloric acid, HCl, dissociates in water to yield the required hydrogen ions, H + , and also chloride ions, Cl - Â . The base sodium hydroxide, NaOH, dissociates in water to yield the required hydroxide ions, OH - , and also sodium ions, Na + . The BrÃ¶nsted-Lowry Theory Some substances act as acids or bases when they are dissolved in solvents other than water, such as liquid ammonia. The BrÃ¶nsted-Lowry theory, named for the Danish chemist Johannes BrÃ¶nsted and the British chemist Thomas Lowry, provides a more general definition of acids and bases that can be used to deal both with solutions that contain no water and solutions that contain water. It defines an acid as a proton donor and a base as a proton acceptor. In the BrÃ¶nsted-Lowry theory, water, H 2 O, can be considered an acid or a base since it can lose a proton to form a hydroxide ion, OH - , or accept a proton to form a hydronium ion, H 3 O + (see amphoterism ). When an acid loses a proton, the remaining species can be a proton acceptor and is called the conjugate base of the acid. Similarly when a base accepts a proton, the resulting species can be a proton donor and is called the conjugate acid of that base. For example, when a water molecule loses a proton to form a hydroxide ion, the hydroxide ion can be considered the conjugate base of the acid, water. When a water molecule accepts a proton to form a hydronium ion, the hydronium ion can be considered the conjugate acid of the base, water. The Lewis Theory Another theory that provides a very broad definition of acids and bases has been put forth by the American chemist Gilbert Lewis. The Lewis theory defines an acid as a compound that can accept a pair of electrons and a base as a compound that can donate a pair of electrons. Boron trifluoride, BF 3 , can be considered a Lewis acid and ethyl alcohol can be considered a Lewis base.
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Answers:Aluminum hydroxide (Amphojel , AlternaGEL ) Magnesium hydroxide (Phillips Milk of Magnesia) Aluminum hydroxide and magnesium hydroxide (Maalox , Mylanta ) Aluminum carbonate gel (Basaljel ) Calcium carbonate (Alcalak , Calcium Rich Rolaids , Quick-Eze , Rennie , Titralac , Tums ) Sodium bicarbonate (Bicarbonate of soda, Alka-Seltzer ) Hydrotalcite (Mg6Al2(CO3)(OH)16 4(H2O); Talcid ) Bismuth subsalicylate (Pepto-Bismol) Magaldrate + Simethicone (Pepsil)
Answers:Acids: HNO3, HCl, H2SO4, H2O, NH4+ Bases: NaOH, NH3,
Answers:http://forum.purseblog.com/general-discussion/anyone-good-in-chemistry-330196.html http://www.justanswer.com/questions/30vvx-trying-to-understand-acids-bases-and-salts-i-understand http://chestofbooks.com/health/materia-medica-drugs/Treatise-Therapeutics-Pharmacology-Materia-Medica-Vol2/3-Effects-And-Uses-Of-Alkalies-As-Dynamic-Agents.html http://www.lef.org/protocols/prtcl-027.shtml ====================================================== Acids: ascorbic acid, , gamma-amino-butyric acid Alpha-Lipoic Acid--is a powerful antioxidant that regulates gene expression and preserves hearing during cisplatin therapy Bases: magnesium hydroxide (Milk of magnesia) , sodium bicarbonate, calcium carbonate (Rolaids)(Bronsted base) ==================================================== Salts: sodium chloride, potassium chloride, sodium fluoride Ascorbic acid (vitamin C) can be taken internally to neutralize "free radicals," otherwise known as non-essential ionic compounds and play a role in natural metabolism. & treatment for Scurvey Sodium bicarbonate reduces stomach acids and can make the urine less acidic. It is used as an antacid to treat heartburn, indigestion, and other stomach disorders. It is also used to treat various kidney disorders and to increase the effectiveness of sulfonamides. Sodium fluoride is used in dental products to fortify hydroxyapatite composing the enamelin found in teeth to prevent cavities.
Answers:I'll answer your biological problem first. First, your stomach contains HCl. That's right, hydrochloric acid. The pH is usually around 3-4 or so. A very potent acid. And the main reason why we have it is to kill any bacteria in our food. Bacteria are really prone to pH changes, and since your mouth is slightly basic, your acidic stomach environment will almost instantly kill nearly all bacteria. It's a line of defense. Now, acid and bases are used quite a lot in nature. As described above, your mouth is basic. Also, your blood contains what's called a buffer. That is, carbonic acid. It breaks down and is reconstructed to keep your blood pH around 7.4. Not to mention that your muscles release lactic acid when they're strained. I hope those are enough examples