ACIDS AND BASES

Acids and Bases: Comprehensive Study Notes

Arrhenius Definition of Acids and Bases

  • Arrhenius Acids:

    • First definition of an acid.

    • Definition: A substance that produces hydrogen ions (H+H^+) when dissolved in water.

    • H+H^+ equivalent to a proton: An atom with atomic number 1 (Hydrogen) and no electron gives it a positive charge.

    • Example: Hydrogen Chloride (HCl) ionizes in water:

      • HCl(g)→H+(aq)+Cl−(aq)HCl (g) \rightarrow H^+ (aq) + Cl^- (aq)

    • Common Arrhenius Acids:

      • HCl (Hydrochloric Acid)

      • HNO3HNO_3 (Nitric Acid)

      • H<em>2SO</em>4H<em>2SO</em>4 (Sulfuric Acid)

      • CH3COOHCH_3COOH (Acetic Acid)

  • Arrhenius Bases:

    • Definition: A substance that produces hydroxide ions (OH^-$) when dissolved in water.

    • Example: Sodium Hydroxide (NaOH) dissolves in water:

      • NaOH (s) \rightarrow Na^+ (aq) + OH^- (aq)</p></li></ul></li><li><p><strong>CommonArrheniusBases:</strong></p><ul><li><p>NaOH(SodiumHydroxide)</p></li><li><p>KOH(PotassiumHydroxide)</p></li><li><p></p></li></ul></li><li><p><strong>Common Arrhenius Bases:</strong></p><ul><li><p>NaOH (Sodium Hydroxide)</p></li><li><p>KOH (Potassium Hydroxide)</p></li><li><p>NH_3(Ammonia)</p></li></ul></li></ul></li></ul><h4id="1c7515cf−45ba−4d0b−8895−5912f989a615"data−toc−id="1c7515cf−45ba−4d0b−8895−5912f989a615"collapsed="false"seolevelmigrated="true">Brønsted−LowryAcidsandBases</h4><ul><li><p><strong>Brønsted−LowryDefinition:</strong></p><ul><li><p><strong>Acid:</strong>Asubstancethatdonatesaproton(hydrogenion,(Ammonia)</p></li></ul></li></ul></li></ul><h4 id="1c7515cf-45ba-4d0b-8895-5912f989a615" data-toc-id="1c7515cf-45ba-4d0b-8895-5912f989a615" collapsed="false" seolevelmigrated="true">Brønsted-Lowry Acids and Bases</h4><ul><li><p><strong>Brønsted-Lowry Definition:</strong></p><ul><li><p><strong>Acid:</strong> A substance that donates a proton (hydrogen ion,H^+)inachemicalreaction.</p></li><li><p><strong>Base:</strong>Asubstancethatacceptsaprotoninachemicalreaction.</p></li></ul></li><li><p><strong>ProtonTransfer:</strong>ReactionsbetweenBrønsted−Lowryacidsandbasesinvolvethetransferofaproton.</p></li><li><p><strong>ConjugateAcid−BasePairs:</strong></p><ul><li><p>Whenmoleculesorionsarerelatedbythelossorgainofone) in a chemical reaction.</p></li><li><p><strong>Base:</strong> A substance that accepts a proton in a chemical reaction.</p></li></ul></li><li><p><strong>Proton Transfer:</strong> Reactions between Brønsted-Lowry acids and bases involve the transfer of a proton.</p></li><li><p><strong>Conjugate Acid-Base Pairs:</strong></p><ul><li><p>When molecules or ions are related by the loss or gain of oneH^+,theyformaconjugateacid−basepair.</p></li><li><p>A<strong>base</strong>formsits<strong>conjugateacid</strong>(whichhasonemore, they form a conjugate acid-base pair.</p></li><li><p>A <strong>base</strong> forms its <strong>conjugate acid</strong> (which has one moreH^+).</p></li><li><p>An<strong>acid</strong>formsits<strong>conjugatebase</strong>(whichhasoneless).</p></li><li><p>An <strong>acid</strong> forms its <strong>conjugate base</strong> (which has one lessH^+).</p></li></ul></li><li><p><strong>Examples:WritetheconjugateacidforthefollowingBrønsted−Lowrybases:</strong></p><ul><li><p>).</p></li></ul></li><li><p><strong>Examples: Write the conjugate acid for the following Brønsted-Lowry bases:</strong></p><ul><li><p>HS^- \rightarrow H_2S(conjugateacid)</p></li><li><p>(conjugate acid)</p></li><li><p>NO2^- \rightarrow HNO2(conjugateacid)</p></li><li><p>(conjugate acid)</p></li><li><p>HPO4^{2-} \rightarrow H2PO_4^-(conjugateacid)</p></li></ul></li><li><p><strong>Examples:WritetheconjugatebasesforthefollowingBrønsted−Lowryacids:</strong></p><ul><li><p>(conjugate acid)</p></li></ul></li><li><p><strong>Examples: Write the conjugate bases for the following Brønsted-Lowry acids:</strong></p><ul><li><p>HCO3^- \rightarrow CO3^{2-}(conjugatebase)</p></li><li><p>(conjugate base)</p></li><li><p>H3PO4 \rightarrow H2PO4^-(conjugatebase)</p></li><li><p>(conjugate base)</p></li><li><p>H2SO4 \rightarrow HSO_4^-(conjugatebase)</p></li></ul></li><li><p><strong>DissolvingHClinwater(Brønsted−Lowryperspective):</strong></p><ul><li><p>Water((conjugate base)</p></li></ul></li><li><p><strong>Dissolving HCl in water (Brønsted-Lowry perspective):</strong></p><ul><li><p>Water (H_2O)actsasabasebyacceptingaprotonfromHCl.</p></li><li><p>ThereactionshowsthetransferofaprotonfromHCltowater:</p><ul><li><p>) acts as a base by accepting a proton from HCl.</p></li><li><p>The reaction shows the transfer of a proton from HCl to water:</p><ul><li><p>HCl + H2O \rightarrow H3O^+ + Cl^-</p></li></ul></li><li><p><strong>Noteon</p></li></ul></li><li><p><strong>Note onH^+inwater:</strong>Aproton(in water:</strong> A proton (H^+)doesnotexistindependentlyinwater.Itsstrongattractiontopolarwatermoleculescausesittobondwithwater,forminga<strong>hydroniumion</strong>() does not exist independently in water. Its strong attraction to polar water molecules causes it to bond with water, forming a <strong>hydronium ion</strong> (H_3O^+).</p></li></ul></li><li><p><strong>TwoConjugatePairsinReactions:</strong></p><ul><li><p>Sinceprotonsaretransferredinbothforwardandreversereactions,mostacid−basereactionscontaintwoconjugateacid−basepairs.</p></li><li><p><strong>Examplefromtranscript(identifyconjugateacid−basepairs):</strong></p><ul><li><p>).</p></li></ul></li><li><p><strong>Two Conjugate Pairs in Reactions:</strong></p><ul><li><p>Since protons are transferred in both forward and reverse reactions, most acid-base reactions contain two conjugate acid-base pairs.</p></li><li><p><strong>Example from transcript (identify conjugate acid-base pairs):</strong></p><ul><li><p>NH3 + H2O \rightleftharpoons NH_4^+ + OH^-</p><ul><li><p></p><ul><li><p>H_2O(acid)and(acid) andOH^-(conjugatebase)</p></li><li><p>(conjugate base)</p></li><li><p>NH3(base)and(base) andNH4^+(conjugateacid)</p></li></ul></li><li><p>(conjugate acid)</p></li></ul></li><li><p>HCN + SO4^{2-} \rightleftharpoons CN^- + HSO4^-</p><ul><li><p></p><ul><li><p>HCN(acid)and(acid) andCN^-(conjugatebase)</p></li><li><p>(conjugate base)</p></li><li><p>SO4^{2-}(base)and(base) andHSO4^-$$ (conjugate acid)

Strong and Weak Acids and Bases

  • **Distinction between