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Properties of Acids and Bases

Section 6.1-6.2

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Properties of Acids and Bases

  • Acids and Bases can both be defined empirically and theoretically.

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  • You are expected to be able to provide any of the following definitions and use them to answer questions.

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Empirical Definitions

Acid – a substance which dissolves in water to produce a solution that:

    • Tastes sour
    • Turns blue litmus red
    • Conducts electricity
    • Reacts with active metals to produce H2(g)
    • Neutralizes Bases

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Base – a substance which dissolves in water to produce a solution that:

    • Tastes bitter; feels slippery
    • Turns red litmus blue
    • Conducts electricity
    • Neutralizes acids

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Theoretical Definitions

a) Arrhenius:

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Acid – a substance that forms an acidic solution by dissolving in water to produce free hydrogen ions (H+(aq)) in solution

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    • Example: HCl (aq) πŸ‘ͺ H+ (aq) + Cl- (aq)

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Base – a substance that forms a basic solution by dissolving in water to produce free hydroxide ions (OH-(aq)) in solution

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    • Example: NaOH(aq) πŸ‘ͺ Na+(aq) + OH–(aq)

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Theoretical Definitions

b) Modified Definition:

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Acid – a species that forms an acidic solution by reacting with water to produce hydronium ions (H3O+(aq))

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    • Example: HCl (aq) + H2O(aq)πŸ‘ͺ H3O+(aq) + Cl- (aq)

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Base – a species that forms a basic solution by reacting with water to produce hydroxide ions (OH-(aq))

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    • Example: NH3 (aq) + H2O(aq)πŸ‘ͺ NH4+(aq) + OH–(aq)

The hydronium ion (hydrated proton) – was discovered by Paul GiguΓ¨re at the UniversitΓ© Laval in 1957.

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The Hydronium Ion

  • Theoretical chemists thought it was unlikely that a hydrogen ion, which is a tiny proton with a very high charge-to-size ratio, could exist on its own in aqueous solution.

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  • Instead they thought it would bond strongly to polar water molecules.

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  • Paul GiguΓ¨re provided empirical evidence for this type of bonding when he discovered hydrated protons (H3O+(aq)); commonly called hydronium ions

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  • The modern view of acids and bases is that the hydronium ions (H3O+(aq)); are responsible for acidic properties and hydroxide ions (OH–(aq)) are responsible for basic properties

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Learning Tips:

  • The terms β€œacid” and β€œbase” refer to chemical substances, whereas the terms β€œacidic” and β€œbasic” refer to the properties of a solution

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  • Chemists have known about some acids for hundreds of years. Because these acids are commonly known by familiar names, their IUPAC names are not often used. You should know both forms of naming for acids.

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  • Do you remember how to name acids?

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Naming Acids

  • Systematic IUPAC

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  1. aqueous hydrogen chloride

HCl (aq)

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  1. aqueous hydrogen chlorate

HClO3(aq)

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  1. aqueous hydrogen chlorite

HClO2(aq)

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  • Traditional

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  1. hydrogen ______ide = hydro______ic acid

ex. hydrogen chloride = hydrochloric acid

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  1. hydrogen ______ate = __________ic acid

ex. hydrogen chlorate = chloric acid

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  1. hydrogen ______ite = __________ous acid

ex. hydrogen chlorite = chlorous acid

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Remember: acid contains sulfur = you add a ur H2SO4(aq) sulfuric acid

acid contains phosphorus = add an or H3PO4(aq) phorphoric acid

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Practice – Naming Acids

IUPAC

    • HClO4(aq)
    • HClO(aq)
    • HNO2(aq)
    • HNO3(aq)
    • H2SO4(aq)
    • H2SO3(aq)
    • H3PO4(aq)

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Traditional

aqueous hydrogen perchlorate

aqueous hydrogen hypochlorite

aqueous hydrogen nitrite

aqueous hydrogen nitrate

aqueous hydrogen sulfate

aqueous hydrogen sulfite

aqueous hydrogen phosphate

perchloric acid

hypochlorous acid

nitrous acid

nitric acid

sulfuric acid

sulfurous acid

phosphoric acid

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Homework

  • Read pg. 234-237

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  • Do pg. 237 #1-5, 7