[Skip to Content](https://www.sigmaaldrich.com#main-content) [![MilliporeSigma](https://www.sigmaaldrich.com/static/logos/purple/millipore_sigma.svg)](https://www.sigmaaldrich.com/US/en) Products Cart0 USEN Products ProductsApplicationsServicesResourcesSupport [Login / Register](https://www.sigmaaldrich.com/oidc-sign-in) [Order Lookup](https://www.sigmaaldrich.com/US/en/order-lookup) [Quick Order](https://www.sigmaaldrich.com/US/en/quick-order) Cart0 [Home](https://www.sigmaaldrich.com/US/en)[Organic Reaction Toolbox](https://www.sigmaaldrich.com/US/en/applications/chemistry-and-synthesis/synthetic-methods/organic-reaction-toolbox)Acid and Base Chart — Table of Acids & Bases # Acid and Base Chart — Table of Acids & Bases ## Relative Strength of Acids & Bases Use this acids and bases chart to find the relative strength of the most common acids and bases. This acid-base chart includes the *K*a value for reference along with the chemical's formula and the acid’s conjugate base. The acid and base chart is a reference table designed to make determining the strength of acids and bases simpler. This chart is ideal for use in the lab or in the classroom. ### Table of Acid and Base Strength __Acid__   __Base__   __Strength of Acid____Ka____Name____Formula____Formula____Name____Strength of Base__ StrongestLargePerchloric acidHClO4ClO4-Perchlorate ionWeakest  3.2 * 109Hydroiodic acidHII-Iodide   1.0 * 109Hydrobromic acidHBrBr-Bromide   1.3 * 106Hydrochloric acidHClCl-Chloride   1.0 * 103Sulfuric acidH2SO4HSO4-Hydrogen sulfate ion   2.4 * 101Nitric acidHNO3NO3-Nitrate ion   --------Hydronium ionH3O+H2OWater   5.4 * 10-2Oxalic acidHO2C2O2HHO2C2O2-Hydrogen oxalate ion   1.3 * 10-2Sulfurous acidH2SO3HSO3-Hydrogen sulfite ion   1.0 * 10-2Hydrogen sulfate ionHSO4 -SO4 2-Sulfate ion   7.1 * 10-3Phosphoric acidH3PO4H2PO4-Dihydrogen phosphate ion   7.2 * 10-4Nitrous acidHNO2NO2-Nitrite ion   6.6 * 10-4Hydrofluoric acidHFF-Fluoride ion   1.8 * 10-4Methanoic acidHCO2HHCO2-Methanoate ion   6.3 * 10-5Benzoic acidC6H5COOHC6H5COO-Benzoate ion  Medium5.4 * 10-5Hydrogen oxalate ionHO2C2O2-O2C2O2 2-Oxalate ionMedium  1.8 * 10-5Ethanoic acidCH3COOHCH3COOEthanoate (acetate) ion   4.4 * 10-7Carbonic acidH2CO3HCO3 -Hydrogen carbonate ion   1.1 * 10-7Hydrosulfuric acidH2SHSO3-Hydrogen sulfide ion   6.3 * 10-8Dihydrogen phosphate ionH2PO4 -HPO4 2-Hydrogen phosphate ion   6.2 * 10-8Hydrogen sulfite ionHS-SO32-Sulfite ion   2.9 * 10-8Hypochlorous acidHClOClO-Hypochlorite ion   6.2 * 10-10Hydrocyanic acidHCNCN-Cyanide ion   5.8 * 10-10Ammonium ionNH4 +NH3Ammonia   5.8 * 10-10Boric acidH3BO3H2BO3-Dihydrogenborate   4.7 * 10-11Hydrogen carbonate ionHCO3 -CO3 2-Carbonate ion   4.2 * 10-13Hydrogen phosphate ionHPO4 2-PO4 3-Phosphate ion   1.8 * 10-13Dihydrogen borate ionH2BO3 -HBO3 2-Hydrogen borate ion   1.3 * 10-13Hydrogen sulfide ionHS-S 2-Sulfide ion   1.6 * 10-14Hydrogen borate ionHBO3 2-BO3 3-Borate ion  Weakest-WaterH2OOH-HydroxideStrongest ## How to Use the Acid & Base Chart [](https://www.sigmaaldrich.com)Read these instructions to learn how to use this acids and bases chart. The table lists the *K*a values and the strength of each acid and base. 1. Strong acids are listed at the top left-hand corner of the table and have Ka values >1 2. Acids with a *K*a value less than one are considered weak and get weaker as we move to the bottom of the table. 3. The strong bases are listed at the bottom-right of the table and get weaker as we move to the top of the table. ## Conjugate Acid-Base Pairs In this chart, the strongest acids are at the top left, and the weakest bases are at the top right. The conjugate base of a strong acid is a weak base; therefore, the conjugate acid of a strong base is a weak acid. ## Acid-Base Pairs and Buffer Chemistry A [buffer solution](https://www.sigmaaldrich.com/US/en/technical-documents/protocol/protein-biology/protein-concentration-and-buffer-exchange/buffer-reference-center) contains a weak acid and its conjugate base or a weak base and its conjugate acid. Buffers work by reacting with a base or acid to control the pH of a solution. ## [](https://www.sigmaaldrich.com)Download the Acid & Base Chart [Acid & Base Chart Image](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/chemistry-and-synthesis/organic-reaction-toolbox/acids-and-bases-chart-ms.png) [Acid & Base Chart PDF](https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/marketing/global/documents/830/474/acids-and-bases-chart-ms.pdf) ## Products Sorry, an unexpected error has occurred Response not successful: Received status code 500 __Related Articles__ - [Acid & Base Normality and Molarity Calculator](https://www.sigmaaldrich.com/US/en/support/calculators-and-apps/molarity-calculator) - [Buffer Reference Center](https://www.sigmaaldrich.com/US/en/technical-documents/protocol/protein-biology/protein-concentration-and-buffer-exchange/buffer-reference-center) - [Solution Dilution Calculator](https://www.sigmaaldrich.com/US/en/support/calculators-and-apps/solution-dilution-calculator) - [Caustic Alkalis & Bases](https://www.sigmaaldrich.com/US/en/products/chemistry-and-biochemicals/lab-chemicals/caustic-alkalis-and-bases) - [Acids for laboratory, analysis, and regulated applications](https://www.sigmaaldrich.com/US/en/products/chemistry-and-biochemicals/lab-chemicals/acids) - [Role of High Purity Metal Salts in Chemical Synthesis](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/chemistry-and-synthesis/ch-functionalization/role-of-high-purity-metal-salts-in-chemical-synthesis) - [Metal Impurities in API Synthesis and Drug Quality](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/chemistry-and-synthesis/cross-coupling/metal-impurities-in-api-synthesis-and-drug-quality) - [1-hydrosilatrane](https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/chemistry-and-synthesis/organic-reaction-toolbox/1-hydrosilatrane) - [View More](https://www.sigmaaldrich.com/US/en/search/facet-search?focus=sitecontent&term=facet-search) __Related Product Categories__ - [Acids for laboratory, analysis, and regulated applications](https://www.sigmaaldrich.com/US/en/products/chemistry-and-biochemicals/lab-chemicals/acids) - [Caustic Alkalis & Bases](https://www.sigmaaldrich.com/US/en/products/chemistry-and-biochemicals/lab-chemicals/caustic-alkalis-and-bases) Top __Sign In To Continue__ To continue reading please sign in or create an account. 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