1. Weak acid can produce strong acid In the law of complex decomposition reaction, generally only strong acid can produce weak acid.
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However, hydrochloric acid can be produced by dropping hydrogenated sulfuric acid into CuCl2 solution: CuCl2 H2S==CuS↓ 2HCl, which is an abnormal situation of weak acid to strong acid. CuS is insoluble in strong acids. The reaction 3NaI H3PO4(concentrated) = Na3PO4 3HI↑ can occur because it conforms to the law of producing low-boiling acids from high-boiling acids. In addition, H2SO3 can be oxidized to H2SO4 by HNO3, HClO, FeCl3 and other solutions.
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2. Typical reaction of weak base to strong base
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Marked no 2NH3·H2O=Ag(NH3)2OH 2H2O
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②Ca (OH) 2 Na2CO3 = CaCO3↓2NaOH
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Reaction ① belongs to the complexation reaction, and the reason why the reaction can occur is that the complexation ability of Ag and NH3 is strong. Reaction (2) belongs to the complex decomposition reaction, and the reason why the reaction can occur is that there is the precipitation of CaCO3 which is insoluble in water.
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3. Alkali can also react with alkali
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Under normal circumstances, the base does not react with the base, but some insoluble bases with strong complexation ability may be dissolved in weak alkali ammonia water. Such as AgOH 2NH3·H2O=Ag(NH3)2OH 2H2O.
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4. Acid can also react with acid
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In general, acids do not react with acids, but oxidizing acids can react with reducing acids. For example, nitric acid can react with hydroiodic acid, hydrobromic acid, hydrosulfuric acid, and sulfite; Concentrated sulfuric acid can react with hydroiodic acid, hydrobromic acid and hydrosulfuric acid. Hypochlorous acid can react with hydrochloric acid and sulfite. Sulfite can react with hydrosulfuric acid, etc.
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5. Acid oxides can also react with acids
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Under normal circumstances, acidic oxides do not react with acids, but the following reactions are abnormal: SO2 2H2S==3S↓ 2H2O, SiO2 4HF =SiF4↑ 2H2O. The reason is that the former is a REDOX reaction, and the latter is the generation of gas, which is conducive to the reaction.
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6. Substances with weak reducing properties can be made into substances with strong reducing properties
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The basic law of the comparison of oxidative reducibility in the REDOX reaction is as follows:
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Oxidation strength: Oxidizer > Oxidation product
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Reducibility: Reductant > Reduction product
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However, in the industrial silicon reaction, the weak reducing carbon can produce the strong reducing silicon, because the above rules only apply to the solution, 2C+SiO22CO↑+Si, and this reaction is the gas phase reaction at high temperature. For example, the reducibility of potassium is stronger than sodium, and the reducibility of rubidium is stronger than calcium, but the industry can use Na to make K and Ca to make Rb, because the boiling point of K is lower than Na, and the boiling point of Rb is lower than Ca, and the reaction temperature can be controlled so that K and Rb escape as steam, so that the concentration of the product is reduced, and the reaction is carried out in the positive direction.
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7. The metal behind the hydrogen in the metal activity sequence table can also replace the hydrogen in the acid
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In general, only the metal in front of the hydrogen can replace the acid or the hydrogen in water. However, Hg and Ag can react as follows:
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Hg H2S==HgS H2↑
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2agbr H2S = = Ag2S H2↑
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The reason is that the solubility of HgS and Ag2S is very small, which is conducive to the chemical reaction moving in the positive direction.
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8. The gold or nonmetallic properties of the elements are strong, and their elemental qualities are not active
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In general, the gold or nonmetallic properties of the elements are stronger, and the more active their elemental qualities are. However, for a few elements, the atoms and their elemental activity show a mismatch relationship. For example, lead is stronger than tin, but tin is in front of lead in the metal activity sequence table. The reason is that the conditions of comparison are different, the former means that lead is easier than tin when gaseous atoms lose electrons, while the latter means that tin is easier than lead to lose electrons in solution; O is more nonmetallic than Cl, but O2 is more stable than Cl2, N is more nonmetallic than P, but N2 is much more stable than phosphorus, and N2 can even replace the noble gas, because the degree of chemical bonding in the elemental molecule affects the properties of the molecule.
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9. Active metals or non-metallic elements in the solution cannot replace inactive metals or non-metals
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In general, active metals or non-metallic elements can replace inactive metals or non-metals in solution. However, Na, K and other very active metals can not replace relatively inactive metals from their salt solution; F2 cannot displace Cl, Br and I from its salt solution. The reason is that in an aqueous solution, the ions and water form hydrated ions completely surrounded by water molecules, and the very reactive elements first undergo a displacement reaction with the solvent water.
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10. S is easier to react with Hg and Ag than O2
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Generally, the stronger the oxidation or reducibility, the stronger the reaction, and the easier the conditions. When O2 and S react with metals separately, O2 is generally easier. However, when they react with Hg and Ag, sulfur can react with Hg and Ag at room temperature.
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11. Oxygen is non-metallic, but it can exist in nature in a free state, and oxygen has no positive valence.
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12. Oxygen is more active than sulfur, but sodium can burn quietly in oxygen, and it explodes when mixed with sulfur
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Sulfur burns in oxygen and gives off heat easily, and it is not easy to lose heat when mixed with sodium, so it explodes.
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13. The volume ratio of nitrogen and oxygen in the air is about 4:1, but the combustion of magnesium strips in the air mainly produces magnesium oxide rather than magnesium nitride
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The direction of the reaction depends not on the amount of reactants, but on the properties of the reactants. Since oxygen is more reactive than nitrogen, the main product is magnesium oxide rather than magnesium nitride.
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14.Ca is more active than Na, but Na reacts more vigorously with water than Ca
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Ca reacts with water to form a slightly water-soluble Ca(OH)2 covering the surface of Ca, reducing the chemical reaction rate.
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15. Both diamond and graphite contain carbon-carbon covalent bonds, but the melting point of graphite is higher than that of diamond
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Although diamond graphite has carbon-carbon covalent bonds, in addition to carbon-carbon single bonds, each carbon atom will form a large delocalized π bond with other carbon atoms.
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16. The conditions of the compound decomposition reaction are the formation of insoluble substances or gases or weak electrolytes, but baking soda soluble in water is generated in the Hou alkaline process
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Although baking soda can be dissolved in water, but the solubility is small, in the saturated sodium chloride solution into ammonia and carbon dioxide conditions, it is quite unacceptable. This conforms to the law of ionic reaction.
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17. Increasing the concentration of reactants increases the conversion rate
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Increase the concentration of reactant A, then the conversion rate of A generally decreases, but for the reaction: 2NO2(gas) N2O4 (gas) when it reacts in a closed container with a fixed volume, if the concentration of NO2 is increased, the pressure in the system increases, so that the equilibrium moves in the direction of the gas volume reduction, that is, the equilibrium moves to the right. At this time, the conversion rate of NO2 does not decrease, but increases.
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18. Anhydride is not an oxide
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Acid anhydrides are generally oxides, but the anhydrides of organic acids are often not oxides.
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19. CO2 can be prepared by reacting CaCO3 with dilute sulfuric acid or concentrated hydrochloric acid
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In the third grade, it was especially emphasized that CaCO3 and CaCO3 could not be used to produce carbon dioxide. The reason was that CaSO4, slightly soluble in water, was formed when calcium carbonate reacted with dilute sulfuric acid and covered the surface of cacO3, thus preventing further reaction. The reason for not using concentrated hydrochloric acid is that concentrated hydrochloric acid is volatile, so that the generated carbon dioxide is mixed with impurities HCl. But if we ground calcium carbonate into a powder, the reaction can happen very smoothly. In the same way, carbon dioxide gas made from concentrated hydrochloric acid and calcium carbonate can be passed through a washing cylinder saturated with NaHCO3, so that the impurity hydrogen chloride can be removed, and the carbon dioxide will not dissolve.
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20. Laboratory preparation of HCl can also be used. Solid + solid → gas " Device of
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In fact, we can use NaCl to react with NaHSO4 to produce HCl, but the temperature should be controlled at about 500 ~ 600℃, NaCl NaHSO4=Na2SO4 HCl↑
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21. Reactions in which elemental substances are involved or produced are not REDOX reactions
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Such as transitions between allotropes. Because the structure of each other's allotropes is different, the transformation between them involves the breaking and formation of chemical bonds.
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22.SO2 can bleach common organic pigments and some indicators, but can not bleach litmus test liquid, but can only turn litmus test liquid red.
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23. Related properties of halogens and their compounds
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The general formula of the reaction of halogen with water is: X2 H2O=HX HXO, while the reaction of F2 with water gives off O2; Other silver halides are insoluble in water and photosensitive, while AgF is insoluble in water and photosensitive. Other calcium halides are soluble in water, while CaF is insoluble in water. F has no positive valence and can not form an oxygenic acid; Different substances containing different valence states of the same element, generally the higher the valence state, the stronger the oxidation, but each oxygen containing acid of chlorine is the lower the valence state, the stronger the oxidation.
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24. Anomalous properties of silicon
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Silicon is very stable at room temperature, but there is no free silicon in nature and only the combined state, because silicon is more stable in the combined state.
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Generally, only the active metal in front of the hydrogen can replace the hydrogen in the acid or water, but the non-metallic silicon reacts with a strong alkali solution to produce H2.
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The reason is that silicon exhibits a certain gold property, and hydrogen is generated by the reduction of hydroionization H under alkali action.
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Non-metal can not replace hydrogen in acid, but silicon can replace hydrogen in hydrofluoric acid. Silicon is more reductive than carbon, and carbon can reduce silicon from silicon dioxide at high temperatures.
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Anhydride can generally react with water to produce the corresponding acid, silica is the anhydride of silicic acid, but can not react with water to produce silicic acid, generally with soluble silicate and acid to prepare;
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Nonmetallic oxides are generally molecular crystals, while silica is atomic crystals.
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Inorganic acids are generally soluble in water, while silicic acid and orthosilicic acid are difficult to dissolve in water.
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Carbonic acid is more acidic than silicic acid, but the reaction can be carried out because the reaction is not carried out in an aqueous solution;
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Silicate aqueous solution is commonly known as water glass, but its chemical composition and glass are not the same;
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An aqueous solution of sodium silicate is also called pholasine, but sodium silicate is a salt rather than a base.
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25. Iron, aluminum and concentrated sulfuric acid, concentrated nitric acid passivation
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At room temperature, iron and aluminum react with dilute sulfuric acid and dilute nitric acid respectively, while concentrated sulfuric acid or concentrated nitric acid can passivate iron and aluminum, because concentrated sulfuric acid and concentrated nitric acid have strong oxidation, so that a dense oxide film is generated on their surface.
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26. Reversible reactions in which the number of gas molecules is not equal change the pressure equilibrium without moving
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For the reversible reaction involving gas in the reaction system, the change of pressure and the equilibrium movement should conform to Le Chatelier's principle.
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For example, after a reaction with an unequal number of gas molecules reaches equilibrium, when a noble gas is filled at a constant temperature and constant volume, the pressure increases, but the equilibrium does not move, because the noble gas does not participate in the reaction, and the equilibrium concentration of each substance does not change.
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27. Strong alkali and weak acid salt solution is acidic
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The method of determining the acid-alkalinity of the solution after hydrolysis of salts is as follows: who is weak and who is hydrolyzed, who is strong and who is characteristic, and the strong and weak acid brine is generally alkaline after hydrolysis. However, NaHSO3 and NaH2PO4 solutions are acidic because their degree of ionization is greater than their degree of hydrolysis.
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28. The negative electrode of a less active metal or non-metal galvanic cell
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In galvanic cells, a relatively active metal is generally negative. However, in the primary cell composed of Mg, Al electrode and NaOH solution, the negative Al is extremely inactive, but not Mg, because Mg does not react with NaOH solution. In the primary cell composed of Fe, Si electrodes and NaOH solution, the negative electrode is Si rather than Fe, because Fe does not react with NaOH solution; In a primary cell composed of Fe, Cu electrodes and concentrated nitric acid, the negative electrode is Cu rather than Fe, because Fe is passivated at room temperature in the presence of concentrated nitric acid.
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29. Unsaturated bonds in organic matter are difficult to add
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If the organic matter contains unsaturated bonds, such as > When C=O, addition reaction can occur, but > in esters or carboxylic acids; C=O, generally very stable and difficult to add.
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30. Noble gases can also undergo chemical reactions
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Noble gas structure is stable, the nature is not active, but under special conditions can also occur chemical reactions, the world has synthesized a variety of compounds containing noble gas elements. Such as XeF2, XeF4 and so on.
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The nucleus of 31.11H has only one proton.
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32. The physical properties of matter are abnormal
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(1) Among the elements of the main VA group, the melting point of the single element tends to rise from top to bottom, but the melting point of bismuth is lower than that of antimony; Among the main IVA group elements, the melting point of tin lead is abnormal.
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Abnormal state of three substances (mercury, potassium-sodium alloy, water) at normal temperature.
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Transition element metals usually have a higher melting point, while Hg is liquid at room temperature and has the lowest melting point of all metals.
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Alloys are usually solid, while potassium-sodium alloys are liquid.
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Nonmetallic hydrides are usually gaseous, whereas the hydride of oxygen, water, is liquid. Hydride melting point anomaly.
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For similar structures, the higher the relative molecular mass, the higher the boiling point, but in the same series of hydrides, the boiling point of HF, H2O, NH3 is abnormal, because they are easy to form hydrogen bonds.
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(2) Abnormal boiling point Among IVA main group elements, the boiling point of silicon and germanium is abnormal; Among the main elements of VA group, antimony and bismuth have abnormal boiling points.
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(3) Abnormal density of alkali metal elements increased from top to bottom, but potassium abnormal; Among the carbon group elements, the density of diamond and crystalline silicon is abnormal.
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(4) Abnormal electrical conductivity General non-metal electrical conductivity is poor, but graphite is a good conductor, C60 can be a superconducting material.
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(5) The solubility of the substance has abnormal at the same temperature, the solubility of the general normal salt is less than its corresponding acid salt. However, the solubility of Na2CO3 is greater than that of NaHCO3. When the temperature changes, the solubility increases with the increase of temperature, but the solubility of Ca(OH)2 decreases with the increase of temperature.
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33. Anomalies in chemical experiments
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When using indicators, the indicator should be prepared into a solution, but the use of pH test paper can not be moistened with water, because the wetting process will dilute the solution and affect the determination of the pH value of the solution;
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The operation of the plastic head dropper should be vertical to 1 ~ 2cm above the mouth of the test tube, otherwise it is easy to dirty the dropper and pollute the reagent. However, when the NaOH solution is added to the FeSO4 solution to prepare Fe(OH)2, in order to prevent the oxidation of the generated Fe(OH)2 into Fe(OH)3 by introducing O2 into the solution, the dropper should not only be extended into the test tube, but also the lower port of the dropper should be inserted below the liquid level.
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34. Anomalous physical properties of matter
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(1) Abnormal melting point of substances: from top to bottom, the melting point of the elements of the main group VA has a tendency to rise, but the melting point of bismuth is lower than that of antimony; Among the main IVA group elements, the melting point of tin lead is abnormal.
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(2) Three substances at room temperature. Transition element metals usually have a higher melting point, while Hg is liquid at room temperature and has the lowest melting point of all metals. Alloys are usually solid, while potassium-sodium alloys are liquid. Nonmetallic hydrides are usually gaseous, whereas the hydride of oxygen, water, is liquid.
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(3) The boiling points of silicon and germanium in IVA main group were abnormal; Among the main elements of VA group, antimony and bismuth have abnormal boiling points.
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(4) Abnormal density
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The density of alkali metals increased from top to bottom, but potassium was abnormal. Among the carbon group elements, the density of diamond and crystalline silicon is abnormal.
The strength of the acid is to see the degree of ionization of H, the higher the ionization process, the stronger! Strong acid to weak acid (sulfuric acid to phosphoric acid), is one of the methods of making acid, there is no volatile acid to volatile acid! (sulfuric acid to hydrochloric acid)