The set of definitions for Bronsted-Lowry Acids and Bases are credited to Johannes Bronsted and Thomas Lowry in 1923.
Concept #1: Bronsted-Lowry Acids and Bases are defined by their donation and acceptance of hydrogen ions respectively.
Example #1: Identify each compound as either Bronsted-Lowry acid or base.
a) NH4+ ____________ c) CH3NH2 __________
b) LiH ___________ d) H2Te ____________
Concept #2: Bronsted-Lowry Acids and Bases Concept 2
Bronsted-Lowry Acids and Bases represent a broader view of acids and bases that don't require an aqueous environment.
Example #2: Identify each compound as either Bronsted-Lowry acid/base, Arrhenius acid/base or both.
a) H2CO3 _______________ d) Sr(OH)2 _______________
b) CH3NH2 _______________ e) HF ___________________
c) KNH2 _________________ f) CaH2 __________________
Concept #3: Bronsted-Lowry Acids and Bases Concept 3
Example #3: Provide formulas of the conjugates for each of the following compounds.
a) NH2NH2 ______________________
b) HCHO2 ______________________
c) HSO4- (base) _________________
d) HClO2 ______________________
A conjugate acid is obtained by adding a hydrogen ion and a conjugate base is obtained by removing a hydrogen ion.
Practice: Identify conjugate acid and conjugate base in the following reaction.
H2PO4− (aq) + H2O (l) ⇌ HPO42− (aq) + H3O+ (aq)
a) HPO42− (conjugate acid), H3O+ (conjugate base)
b) HPO42− (conjugate base), H3O+ (conjugate acid)
c) H2PO4− (conjugate acid), H2O (conjugate base)
d) H2PO4− (conjugate base), H2O (conjugate acid)
Practice: In the following reaction, label Bronsted-Lowry acid and base, along with conjugate acid and base.
H2C6H6O6 (aq) + H2O (l) ⇌ HC6H6O6− (aq) + H3O (aq)
To fully understand the strength of acids and bases relies on also understanding their conjugates.
Concept #4: There is an inverse relationship in strength between acids/bases and their conjugates.
Concept #5: Weak species will create stronger conjugates.
Example #4: Which of the following acids have relatively strong conjugate bases?
a. HBrO4 b. HCN c. HNO3 d. HClO4
Practice: Which of the following is the strongest base?
a. NO3− b. F− c. Cl− d. ClO4− e. H2O
Practice: Which of the following bases will have the weakest conjugate acid?
a. CH3COOH b. KOCH3 c. CH3NH2 d. NH4OH e. LiOH
