Acid dissociation constantMeasure of an acid's strength in solutionIn chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted Ka{\displaystyle K_{a}}) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reactionHA↽−−⇀A−+H+{\displaystyle {\ce {HA <=> A^- + H^+}}}known as dissociation in the context of acid–base reactions.
AcidAn acid is a molecule or ion capable of either donating a proton (i.e. hydrogen cation, H), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid. The first category of acids are the proton donors, or Brønsted–Lowry acids. In the special case of aqueous solutions, proton donors form the hydronium ion H3O and are known as Arrhenius acids.
Equilibrium chemistryEquilibrium chemistry is concerned with systems in chemical equilibrium. The unifying principle is that the free energy of a system at equilibrium is the minimum possible, so that the slope of the free energy with respect to the reaction coordinate is zero. This principle, applied to mixtures at equilibrium provides a definition of an equilibrium constant.
Sulfuric acidChemical compound (H2SO4)Names IUPAC nameSulfuric acidOther names Oil of vitriolHydrogen sulfateDihydrogen sulfateIdentifiers CAS Number7664-93-93D model (JSmol)Interactive imageChEBICHEBI:26836ChEMBLChEMBL572964ChemSpider1086ECHA InfoCard100.028.763EC Number231-639-5E numberE513 (acidity regulators, ...)Gmelin Reference2122 KEGGD05963PubChemCID1118RTECS numberWS5600000UNIIO40UQP6WCFUN number1830 CompTox Dashboard(EPA)DTXSID5029683InChIInChI=1S/H2O4S/c1-5(2,3)4/h(H2,1,2,3,4)Key: QAOWNCQODCNURD-UHFFFAOYSA-NInChI=1/H2O4S/c1-5(2,3)4/h(H2,1,2,3,4)Key: QAOWNCQODCNURD-UHFFFAOYACSMILESOS(=O)(=O)OProperties Chemical formulaH2SO4, sometimes expressed (HO)2SO2 Molar mass98.07 g·mol Appearance Colorless viscous liquid OdorOdorless Density1.8302 g/cm, liquid Melting point10.31 °C (50.56 °F; 283.46 K) Boiling point337 °C (639 °F; 610 K) When sulfuric acid is above 300 °C (572 °F; 573 K), it gradually decomposes to SO3 + H2OSolubility in watermiscible, exothermic Vapor pressure0.001 mmHg (20 °C) Acidity (pKa) pKa1 = strongpKa2 = 2.0 Conjugate baseBisulfateViscosity26.7 cP (20 °C) Structure Crystal structuremonoclinic Space groupC2/c Lattice constanta = 818.1(2) pm, b = 469.60(10) pm, c = 856.3(2) pmα = 90°, β = 111.39(3)°, γ = 90°Formula units (Z)4 Thermochemistry Std molarentropy(S298)157 J/(mol·K) Std enthalpy offormation(ΔfH298)−814 kJ/mol Enthalpy of vaporization(ΔfHvap)56 kJ/mol Hazards GHS labelling: PictogramsSignal wordDangerHazard statementsH290, H314Precautionary statementsP260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501NFPA 704 (fire diamond) 302WOXFlash pointNon-flammable Threshold limit value (TLV)15 mg/m (IDLH), 1 mg/m (TWA), 2 mg/m (STEL) Lethal dose or concentration (LD, LC): LD50 (median dose)2140 mg/kg (rat, oral) LC50 (median concentration)50 mg/m (guinea pig, 8 h)510 mg/m (rat, 2 h)320 mg/m (mouse, 2 h)18 mg/m (guinea pig)LCLo (lowest published)87 mg/m (guinea pig, 2.75 h) NIOSH (US health exposure limits): PEL (Permissible)TWA 1 mg/m REL (Recommended)TWA 1 mg/m IDLH (Immediate danger)15 mg/m Related compounds Related strong acidsSelenic acidHydrochloric acidNitric acidPerchloric acidFluoroantimonic acidChromic acidRelated compoundsSulfurous acidPeroxymonosulfuric acidSulfur trioxideOleumExcept where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).N verify ( ?)
Acetic acidChemical acid found in vinegarSample of acetic acid in a reagent bottleNames Preferred IUPAC nameAcetic acidSystematic IUPAC nameEthanoic acidOther names Vinegar (when diluted); Hydrogen acetate; Methanecarboxylic acid; Ethylic acidIdentifiers CAS Number64-19-73D model (JSmol)Interactive imageAbbreviations AcOH Beilstein Reference506007 ChEBICHEBI:15366ChEMBLChEMBL539ChemSpider171DrugBankDB03166ECHA InfoCard100.000.528EC Number200-580-7E numberE260 (preservatives)Gmelin Reference1380 IUPHAR/BPS1058KEGGC00033D00010MeSHAcetic+acidPubChemCID176RTECS numberAF1225000UNIIQ40Q9N063PUN number2789 CompTox Dashboard(EPA)DTXSID5024394InChIInChI=1S/C2H4O2/c1-2(3)4/h1H3,(H,3,4)Key: QTBSBXVTEAMEQO-UHFFFAOYSA-NSMILESCC(O)=OProperties Chemical formulaCH3COOH Molar mass60.052 g·mol Appearance Colourless liquid OdorOverpowering vinegar-like Density1.049 g/cm (liquid); 1.27 g/cm (solid) Melting point16 to 17 °C; 61 to 62 °F; 289 to 290 K Boiling point118 to 119 °C; 244 to 246 °F; 391 to 392 K Critical point (T, P) 593 K (320 °C), 57.8 bar Solubility in waterMisciblelog P−0.28 Vapor pressure1.54653947 kPa (20 °C) 11.6 mmHg (20 °C) Acidity (pKa) 4.756 Conjugate baseAcetateMagnetic susceptibility (χ)−31.54·10 cm/mol Refractive index (nD)1.371 (VD = 18.19) Viscosity1.22 mPa s 1.22 cP Dipole moment1.74 D Thermochemistry Heat capacity(C)123.1 J/(K⋅mol) Std molarentropy(S298)158.0 J/(K⋅mol) Std enthalpy offormation(ΔfH298)−483.88–483.16 kJ/mol Std enthalpy ofcombustion(ΔcH298)−875.50–874.82 kJ/mol-876.1 kJ/mol Enthalpy of fusion(ΔfHfus)11.7 kJ/mol Enthalpy of vaporization(ΔfHvap)23.7 kJ/mol Pharmacology ATC codeG01AD02 (WHO) S02AA10 (WHO) Legal statusAU: S2 (Pharmacy medicine) / Schedule 6, Schedule 5, Schedule 2 Appendix E, clause 3 Appendix F, clause 4Hazards GHS labelling: PictogramsSignal wordDangerHazard statementsH226, H314Precautionary statementsP280, P305+P351+P338, P310NFPA 704 (fire diamond) 320Flash point40 °C (104 °F; 313 K) Autoignitiontemperature427 °C (801 °F; 700 K) Explosive limits4–16% Lethal dose or concentration (LD, LC): LD50 (median dose)3.31 g/kg, oral (rat) LC50 (median concentration)5620 ppm (mouse, 1 h)16000 ppm (rat, 4 h) NIOSH (US health exposure limits): PEL (Permissible)TWA 10 ppm (25 mg/m) REL (Recommended)TWA 10 ppm (25 mg/m) ST 15 ppm (37 mg/m) IDLH (Immediate danger)50 ppm Related compounds Related carboxylic acidsFormic acidPropionic acidRelated compoundsAcetaldehydeAcetamideAcetic anhydrideChloroacetic acidAcetyl chlorideGlycolic acidEthyl acetatePotassium acetateSodium acetateThioacetic acidSupplementary data page Acetic acid (data page)Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).N verify ( ?)Acid strengthAcid strength is the tendency of an acid, symbolised by the chemical formulaHA, to dissociate into a proton, H, and an anion, A. The dissociation or ionization of a strong acid in solution is effectively complete, except in its most concentrated solutions. HA → H + AExamples of strong acids are hydrochloric acid (HCl), perchloric acid (HClO4), nitric acid (HNO3) and sulfuric acid (H2SO4).
Dissociation (chemistry)Dissociation in chemistry is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into other things such as atoms, ions, or radicals, usually in a reversible manner. For instance, when an acid dissolves in water, a covalent bond between an electronegative atom and a hydrogen atom is broken by heterolytic fission, which gives a proton (H+) and a negative ion. Dissociation is the opposite of association or recombination.
Hydrochloric acidNames IUPAC nameChloraneOther names Muriatic acidSpirits of saltHydronium chlorideChlorhydric acidIdentifiers CAS Number7647-01-0ChEMBLChEMBL1231821ChemSpider307DrugBankDB13366ECHA InfoCard100.210.665EC Number231-595-7E numberE507 (acidity regulators, ...)PubChemCID313monohydrate: 21885828dihydrate: 21899424trihydrate: 21864422hexahydrate: 22077275UNIIQTT17582CBUN number1789 InChImonohydrate: InChI=1S/ClH.H2O/h1H;1H2Key: DKAGJZJALZXOOV-UHFFFAOYSA-Ndihydrate: InChI=1S/ClH.2H2O/h1H;2*1H2Key: NSNHWTBQMQIDCF-UHFFFAOYSA-Ntrihydrate: InChI=1S/ClH.3H2O/h1H;3*1H2Key: CUGZEDSDRBMZMY-UHFFFAOYSA-Nhexahydrate: InChI=1S/ClH.6H2O/h1H;6*1H2Key: VOAPTKOANCCNFV-UHFFFAOYSA-NSMILESmonohydrate: [OH3+].[Cl-]dihydrate: O.[OH3+].[Cl-]trihydrate: O.O.[OH3+].[Cl-]hexahydrate: O.O.O.O.O.[OH3+].[Cl-]Properties Chemical formulaHCl(aq) Molar mass36.46 g·mol Appearance Colorless, transparent liquid, fumes in air if concentrated OdorPungent characteristic Density1.18 g/cm (37%Wt at 20°C) Melting pointConcentration-dependent – see tableBoiling pointConcentration-dependent – see tablelog P0.00 Acidity (pKa) −5.9 (HCl gas) Pharmacology ATC codeA09AB03 (WHO) B05XA13 (WHO) Hazards Occupational safety and health (OHS/OSH): Main hazardsCorrosive, reactive, toxic fumes GHS labelling: PictogramsSignal wordDangerHazard statementsH290, H314, H335Precautionary statementsP234, P261, P271, P280, P303+P361+P353, P305+P351+P338NFPA 704 (fire diamond) 301ACIDFlash pointNon-flammable Related compounds Other anionsHydrofluoric acidHydrobromic acidHydroiodic acidRelated compoundsHydrogen chlorideSupplementary data page Hydrochloric acid (data page)Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).Nverify ( ?)
Perchloric acid60% Perchloric acidNames Systematic IUPAC namePerchloric acidOther names Hyperchloric acidIdentifiers CAS Number7601-90-33D model (JSmol)Interactive imageChEBICHEBI:29221ChEMBLChEMBL1161634ChemSpider22669ECHA InfoCard100.028.648EC Number231-512-4PubChemCID24247RTECS numberSC7500000UNIIV561V90BG2UN number1873 CompTox Dashboard(EPA)DTXSID8047004InChIInChI=1S/ClHO4/c2-1(3,4)5/h(H,2,3,4,5)Key: VLTRZXGMWDSKGL-UHFFFAOYSA-NInChI=1/ClHO4/c2-1(3,4)5/h(H,2,3,4,5)Key: VLTRZXGMWDSKGL-UHFFFAOYADSMILESO[Cl+3]([O-])([O-])[O-]Properties Chemical formulaHClO4Molar mass100.45 g·mol Appearance colorless liquid Odorodorless Density1.768 g/cm Melting point−17 °C (1 °F; 256 K) (72% aqueous solution)−112 °C (anhydrous) Boiling point203 °C (397 °F; 476 K) (azeotrope)75 °C (anhydrous, decomposition) Solubility in waterMiscible Acidity (pKa) −15.2 (±2.0); ≈ −10 Conjugate basePerchlorateHazards Occupational safety and health (OHS/OSH): Main hazardsPowerful oxidizer, highly corrosive, can explosively decompose in high concentrations (or as anhydrous liquid) GHS labelling: PictogramsSignal wordDangerHazard statementsH271, H290, H302, H314, H373Precautionary statementsP210, P280, P303+P361+P353, P304+P340, P305+P351+P338, P310, P371, P375, P380NFPA 704 (fire diamond) 303OXFlash pointNon-flammable Safety data sheet (SDS) ICSC 1006Related compounds Related compoundsHydrochloric acidHypochlorous acidChlorous acidChloric acidPerbromic acidPeriodic acidPermanganic acidPerrhenic acidExcept where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).Yverify ( ?)
Nitric acidNames IUPAC nameNitric acidOther names Aqua fortisSpirit of niterEau forteHydrogen nitrateAcidum nitricumIdentifiers CAS Number7697-37-23D model (JSmol)Interactive imageInteractive imageChEBICHEBI:48107ChEMBLChEMBL1352ChemSpider919ECHA InfoCard100.028.832EC Number231-714-2Gmelin Reference1576 KEGGD02313MeSHNitric+acidPubChemCID944RTECS numberQU5775000UNII411VRN1TV4UN number2031 CompTox Dashboard(EPA)DTXSID5029685InChIInChI=1S/HNO3/c2-1(3)4/h(H,2,3,4)Key: GRYLNZFGIOXLOG-UHFFFAOYSA-NInChI=1/HNO3/c2-1(3)4/h(H,2,3,4)Key: GRYLNZFGIOXLOG-UHFFFAOYAOSMILES[N+](=O)(O)[O-]ON(=O)=OProperties Chemical formulaHNO3Molar mass63.012 g·mol Appearance Colorless liquid OdorAcrid, suffocating Density1.51 g/cm, 1.41 g/cm [68% w/w] Melting point−42 °C (−44 °F; 231 K) Boiling point83 °C (181 °F; 356 K) 68% solution boils at 121 °C (250 °F; 394 K) Solubility in waterMiscible log P−0.13 Vapor pressure48 mmHg (20 °C) Acidity (pKa) −1.4 Conjugate baseNitrateMagnetic susceptibility (χ)−1.99×10 cm/molRefractive index (nD)1.397 (16.5 °C) Dipole moment2.17 ± 0.02 D Thermochemistry Std molarentropy(S298)146 J/(mol·K) Std enthalpy offormation(ΔfH298)−207 kJ/mol Hazards GHS labelling: PictogramsSignal wordDangerHazard statementsH272, H290, H314, H331Precautionary statementsP210, P220, P280, P303+P361+P353, P304+P340+P310, P305+P351+P338NFPA 704 (fire diamond) 302OXFlash pointNon-flammable Lethal dose or concentration (LD, LC): LC50 (median concentration)138 ppm (rat, 30 min) NIOSH (US health exposure limits): PEL (Permissible)TWA 2 ppm (5 mg/m) REL (Recommended)TWA 2 ppm (5 mg/m)ST 4 ppm (10 mg/m) IDLH (Immediate danger)25 ppm Safety data sheet (SDS) ICSC 0183Related compounds Other anionsNitrous acidOther cationsSodium nitratePotassium nitrateAmmonium nitrateRelated compoundsDinitrogen trioxideDinitrogen tetroxideDinitrogen pentoxideNitrogen oxideNitrogen monoxideNitrogen dioxideExcept where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).Yverify ( ?)
IonizationIonization or ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule is called an ion.
Chemical formulaA chemical formula is any of several kinds of notation for expressing the composition and structure of a chemical compound. Chemical formulas use element symbols for the atoms of each chemical element in a compound. There are several conventional types of chemical formula that present different levels of detail.*As an Amazon Associate I earn from qualifying purchases.