7.2 - bronsted-lowry theory of acids and bases

acid

• a substance that neutralises a base forming a salt and water:

acid + base ⇌ salt + water

2HCl (aq) + CaO (s) ⇌ CaCl₂ (aq) + H₂O (l)

• Acids are also substances that release hydrogen ions when they dissolve in water:

HCl(g) → H⁺(aq) + Cl^- (aq)

common acids and what they dissociate into in water

• Hydrochloric acid

  • HCl forms H⁺ + Cl^– in water

• Nitric acid

  • HNO₃ forms H⁺ + NO₃^– in water

• Sulfuric acid

  • H₂SO₄ forms H⁺ + SO₄^2– in water

• Ethanoic acid

  • CH₃COOH forms H⁺ + CH₃COO^– in water

monoprotic acid

an acid that can donate only one proton (hydrogen ion) per molecule in a chemical reaction

inorganic vs organic acid dissociation

• Monoprotic inorganic acids, such as hydrochloric acid, fully dissociate into their ions

• Organic acids, such as carboxylic acids, do not fully dissociate into their ions

  • Only some of the hydrogen atoms can form ions 

base

• A base is a compound that neutralises an acid forming a salt and water

acid + base ⇌{"language":"en","fontFamily":"Times New Roman","fontSize":"18","autoformat":true}" role="math" height="19" width="21" alt="rightwards harpoon over leftwards harpoon" style="box-sizing: border-box; vertical-align: -3px; filter: brightness(0) invert(1); width: 21px; height: 19px;">salt + water

2HCl (aq) + CaO (s) ⇌{"language":"en","fontFamily":"Times New Roman","fontSize":"18","autoformat":true}" role="math" height="19" width="21" alt="rightwards harpoon over leftwards harpoon" style="box-sizing: border-box; vertical-align: -3px; filter: brightness(0) invert(1); width: 21px; height: 19px;">CaCl₂ (aq) + H₂O (l)

• A base is a substance that accepts hydrogen ions or a compound that contains oxide or hydroxide ions

  • For example, when the base ammonia is added to water, the ammonium ion and hydroxide ions are formed:

NH₃ (g) + H₂O (l) → NH₄⁺ (aq) + OH^– (aq)

• For example, when sodium hydroxide is dissolved in solution, sodium ions and hydroxide ions are formed:

NaOH (s) + aq → Na⁺ (aq) + OH^– (aq)

• A base that is soluble in water is called an alkali