Acid-Base Definitions

Question

Identify each of the following reactions as an Arrhenius, Bronstead-Lowry, or Lewis Acid-base reaction. Remember some reactions may fit into multiple categories or may not fit any. In each of the following acid-base reaction, label the acid and the base among the reactant.s

a) Cu2+ + 4Cl- --> CuCl₄^2-

b) Al(OH)₃ + 3HNO₃ --> Al³⁺ + 3H₂O + 3NO₃^-

c) N₂ + 3H₂ --> 2NH₃

d) CN^- + H₂O --> HCN + OH^-

Answer 1

Arrhenius acid reactions produce H⁺ (proton) in an aqueous solution

HCl ---> H⁺ + Cl^-

Arrhenius base reactions produce OH^- (hydroxide ions) in an aqueous solution

NaOH ---> Na⁺ + OH^-

Bronstead-Lowry acid/base reactions involve acid + base and the acid donates a proton to the base forming a conjugate acid (+) and a conjugate base (-)

According to the definition, a Lewis base is a substance that donates electrons and a Lewis acid is a substance that accepts electrons. In this case, the metal cation (Ag+) will act as a Lewis acid by accepting NH3's lone pair of electrons, thus making NH3 a Lewis base. Metal cations have two features that make them good Lewis acids:

1. Their positive charge attracts electrons;
2. They have at least one orbital that can accommodate an electron pair.

a) Cu2+ + 4Cl- --> CuCl₄^2-

No Acids or Bases in equation but Lewis defines acids as any species that accepts an electron, and a base as any specifies that donates an electron

b) Al(OH)₃ + 3HNO₃ --> Al³⁺ + 3H₂O + 3NO₃^-

this equation is broken down into the ions so it is hard so to see

Here is the equation not in ions:

3HNO3 (aq) + Al(OH)3 (s) --> Al(NO3)3 (aq) + 3H2O (l)

The acid donates a hydrogen to the base to make water

c) N₂ + 3H₂ --> 2NH₃

No acids or bases, simple combination reaction

d) CN^- + H₂O --> HCN + OH^-

Can you figure this one out by the examples above?

Answer 2

Arrhenius acid (AA) = proton donor

Arrhenius base (AB) = OH donor

Bronstead acid (BA) = proton donor

Bronstead base (BB) = proton acceptor

Lewis acid (LA) = electron pair acceptor

Lewis base (LB) = electron pair donor

a) Cu2+ + 4Cl- --> CuCl₄^2- Cu2+ = Lewis acid; Cl- = Lewis base

b) Al(OH)₃ + 3HNO₃ --> Al³⁺ + 3H₂O + 3NO₃^- Al(OH)3 = BB; HNO3 = AA and BA

c) N₂ + 3H₂ --> 2NH₃ Not an acid base rx (N2 is a weak LB)

d) CN^- + H₂O --> HCN + OH^- CN- = BB, H2O = BA and AA