Acids and Bases HL
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G. Galvin
Name:
Volumetric Analysis
Objectives
2. Acids and Bases
-relate the properties of acids and bases to their household applications
-recall that neutralisation is the formation of a salt from an acid and a base
-relate their knowledge of neutralisation to everyday examples e.g. use of lime in
agriculture , use of stomach powders
-state the Arrhenius and Brønsted-Lowry theories of acids and bases
-define what is meant by a conjugate acid/base pair
-apply the Arrhenius and Brønsted-Lowry theories of acids and bases for aqueous
solutions only
ARRHENIUS THEORY
Defn: An Arrhenius acid is a substance that dissociates in water to produce H+ ions.
e.g. HCl H+ + Cl- (monobasic as one H+ produced)
H2SO4 2H+ + SO42- (dibasic as two H+ produced)
H3PO4 3H+ + PO43- (tribasic as three H+ produced)
Strong Arrhenius acids dissociate fully in water. e.g. HCl
Weak Arrhenius acids dissociate partially in water. e.g. Ethanoic acid, CH3COOH
Note: H+ ions (which are just protons) cannot exist on their own in water. They bond with a water
molecule to form a hydronium ion, H3O+, as seen in the picture to the right.
Defn: An Arrhenius base is a substance that dissociates in water to produce OH- ions.
e.g. NaOH Na+ + OH-
Mg(OH)2 Mg2+ + 2OH-
Ca(OH)2 Ca2+ + 2OH-
Strong Arrhenius bases dissociate fully in water. e.g. NaOH
Weak Arrhenius bases dissociate partially in water. e.g. Na2CO3
Note: Arrhenius’s theory of acids and bases is limited to solutions dissolved in water. In reality, not all acid-base
reactions need water, or even involve OH- ions. Today, we have a more modern theory for how acids and bases work.
BRØNSTED-LOWRY THEORY
Defn: A Brønsted-Lowry acid is a proton (H+) donor
e.g. HCl + NH3 NH4+ + Cl-
HCl donated a proton to the NH3 and became Cl-. HCl is a Brønsted-Lowry acid
