Question
Which reaction represents an acid–base reaction according to the Lewis theory but not according to the Brønsted–Lowry theory?
A. \({\text{CO}}_3^{2 – }({\text{aq)}} + {{\text{H}}_3}{{\text{O}}^ + }({\text{aq)}} \rightleftharpoons {{\text{H}}_2}{\text{O(l)}} + {\text{HCO}}_3^ – {\text{(aq)}}\)
B. \({\text{C}}{{\text{H}}_3}{\text{COOH(aq)}} + {\text{N}}{{\text{H}}_3}({\text{aq)}} \rightleftharpoons {\text{NH}}_4^ + ({\text{aq)}} + {\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ – }({\text{aq)}}\)
C. \({\text{N}}{{\text{H}}_3}({\text{aq)}} + {\text{HF(aq)}} \rightleftharpoons {\text{NH}}_4^ + ({\text{aq)}} + {{\text{F}}^ – }({\text{aq)}}\)
D. \({\rm{CuS}}{{\rm{O}}_{\rm{4}}}{\rm{(s)}} + 5{{\rm{H}}_{\rm{2}}}{\rm{O(l)}} \rightleftharpoons {\rm{CuS}}{{\rm{O}}_{\rm{4}}}{\rm{ \bullet 5}}{{\rm{H}}_{\rm{2}}}{\rm{O(s)}}\)
▶️Answer/Explanation
D
A Bronsted-Lowry acid is a compound that can donate a hydrogen ion while a Bronsted-Lowry base is a compound that can accept a hydrogen ion.
A Lewis base is a compound that can donate a pair of electrons while a Lewis acid is a compound that can accept a pair of electrons.
The reaction involves the formation of a hydrate of copper sulfate, which can be viewed as a Lewis acid-base reaction but not as a Brønsted-Lowry acid-base reaction.
According to the Lewis theory, an acid is a species that can accept an electron pair, and a base is a species that can donate an electron pair. In the given reaction, the copper ion in copper sulfate can accept electron pairs from the water molecules to form a hydrated complex. Thus, copper sulfate acts as a Lewis acid, while water acts as a Lewis base.
Question
Which of the following is an example of a Lewis acid–base reaction, but not a Brønsted–Lowry acid–base reaction?
A. \({\text{2CrO}}_4^{2 – }{\text{(aq)}} + {\text{2}}{{\text{H}}^ + }{\text{(aq)}} \to {\text{C}}{{\text{r}}_2}{\text{O}}_7^{2 – }{\text{(aq)}} + {{\text{H}}_2}{\text{O(l)}}\)
B. \({\text{Co(}}{{\text{H}}_2}{\text{O)}}_6^{2 + }{\text{(aq)}} + {\text{4HCl(aq)}} \to {\text{CoCl}}_4^{2 – }{\text{(aq)}} + {\text{4}}{{\text{H}}^ + }{\text{(aq)}} + {\text{6}}{{\text{H}}_2}{\text{O(l)}}\)
C. \({\text{N}}{{\text{H}}_3}{\text{(aq)}} + {{\text{H}}^ + }{\text{(aq)}} \to {\text{NH}}_4^ + {\text{(aq)}}\)
D. \({\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ – }{\text{(aq)}} + {{\text{H}}_2}{\text{O(l)}} \to {\text{C}}{{\text{H}}_3}{\text{COOH(aq)}} + {\text{O}}{{\text{H}}^ – }{\text{(aq)}}\)
▶️Answer/Explanation
B
The reaction \({\text{Co(}}{{\text{H}}_2}{\text{O)}}_6^{2 + }{\text{(aq)}} + {\text{4HCl(aq)}} \to {\text{CoCl}}_4^{2 – }{\text{(aq)}} + {\text{4}}{{\text{H}}^ + }{\text{(aq)}} + {\text{6}}{{\text{H}}_2}{\text{O(l)}}\) is a reversible reaction. It involves the formation of a Cobalt chloride ligand, which can be viewed as a Lewis acid-base reaction but not as a Brønsted-Lowry acid-base reaction.
According to the Lewis theory, an acid is a species that can accept an electron pair, and a base is a species that can donate an electron pair. In the given reaction, the cobalt ion in Cobalt chloride ligand can accept electron pairs from the water molecules to form a hydrated complex. Thus, Cobalt chloride ligand acts as a Lewis acid, while water acts as a Lewis base.
Question
In which reaction does \({{\text{H}}_{\text{2}}}{\text{O}}\) act as a Lewis base but not as a Brønsted–Lowry base.
A. \({{\text{H}}_2}{\text{O}} + {\text{NH}}_4^ + \to {{\text{H}}_3}{{\text{O}}^ + } + {\text{N}}{{\text{H}}_3}\)
B. \({{\text{H}}_2}{\text{O}} + {\text{CaO}} \to {\text{C}}{{\text{a}}^{{\text{2}} + }} + {\text{2O}}{{\text{H}}^ – }\)
C. \({{\text{H}}_2}{\text{O}} + {{\text{[Fe(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_6}{\text{]}}^{{\text{3}} + }} \to {\text{Fe[(OH)(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_5}{{\text{]}}^{{\text{2}} + }} + {{\text{H}}_3}{{\text{O}}^ + }\)
D. \({\text{6}}{{\text{H}}_2}{\text{O}} + {{\text{[Ni(N}}{{\text{H}}_3}{{\text{)}}_6}{\text{]}}^{2 + }} \to {\text{6N}}{{\text{H}}_3} + {{\text{[Ni(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_6}{\text{]}}^{2 + }}\)
▶️Answer/Explanation
D
In \({\text{6}}{{\text{H}}_2}{\text{O}} + {{\text{[Ni(N}}{{\text{H}}_3}{{\text{)}}_6}{\text{]}}^{2 + }} \to {\text{6N}}{{\text{H}}_3} + {{\text{[Ni(}}{{\text{H}}_2}{\text{O}}{{\text{)}}_6}{\text{]}}^{2 + }}\) , involves the formation of a hexaaqua Nickel(II)complex, which can be viewed as a Lewis acid-base reaction but not as a Brønsted-Lowry acid-base reaction.
According to the Lewis theory, an acid is a species that can accept an electron pair, and a base is a species that can donate an electron pair. In the given reaction, the Nickel ion in Ni Ammonia complex can accept electron pairs from the water molecules to form a hexaaqua Nickel(II)complex. Thus, Ni Ammonia complex acts as a Lewis acid, while water acts as a Lewis base.
Question
Cobalt forms the complex \({{\text{[Co(N}}{{\text{H}}_{\text{3}}}{{\text{)}}_{\text{5}}}{\text{Cl]}}^{2 + }}\). Which statements are correct for this complex?
I. The cobalt ion acts as a Lewis acid.
II. The cobalt ion has an oxidation number of +II.
III. There are 90° bond angles between the cobalt ion and the ligands.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
▶️Answer/Explanation
B
For oxidation number, Co +5(0)-1=+2
Co = +3.
According to the Lewis theory, an acid is a species that can accept an electron pair. Here, Co ion acts as Lewis acid as it accepts electrons from NH3 and Chloride ions.
is hybridized which result in octahedral geometry. There are 90° bond angles between the cobalt ion and the ligands.
Question
Which definition of a base is correct?
A. A Lewis base accepts a proton.
B. A Brønsted-Lowry base accepts an electron pair.
C. A Brønsted-Lowry base donates an electron pair.
D. A Lewis base donates an electron pair.
▶️Answer/Explanation
D
According to the Lewis theory, an acid is a species that can accept an electron pair, and a base is a species that can donate an electron pair.
A Brønsted-Lowry acid is any species that is capable of donating a proton. A Brønsted-Lowry base is any species that is capable of accepting a proton.