Q18.144 P - Chemistry: Molecular Nature Of Matter And Change

Question

Classify the following as Arrhenius, Bronsted-Lowry, or Lewis acid-base reactions. A reaction may fit all, two, one, or none of the categories:

 $$\begin{gathered} {\text{a)Cu}}^{\text{2}}{\text{ + 4Cl}}^{\text{ - }}\text{ = } {\text{CuCl}}_{\text{4}}^{\text{2 - }} \\ {\text{(b)Al(OH)}}_{\text{3}}{\text{ + 3HNO}}_{\text{3}}\text{ = } {\text{Al}}^{\text{3 + }}{\text{ + 3H}}_{\text{2}}{\text{O + 3NO}}_{\text{3}}^{\text{ - }} \\ {\text{(c)N}}_{\text{2}}{\text{ + 3H}}_{\text{2}}\text{ = } {\text{2NH}}_{\text{3}} \\ {\text{(d)CN}}^{\text{ - }}{\text{ + H}}_{\text{2}}\text{O} \text{ = } {\text{HCN + OH}}^{\text{ - }} \end{gathered}$$

Step-by-Step Solution

Answer

(a) Lewis’s acid-base reaction.

(b) Arrhenius, Bronsted-Lowry, and Lewis acid-base reaction.

(c) Bronsted-Lowry and Lewis acid-base reaction.

(d) Bronsted-Lowry and Lewis acid-base reaction.

Step 1: Concept introduction

A Lewis acid is a chemical species with an empty orbital that can accept an electron pair from a Lewis base and create a Lewis adduct.

Step 2: Finding all three reactions for  Cu 2 +   + 4Cl  -  ⇌ CuCl 2 - 

 ${\text{(a) Cu}}^{\text{2 + }}{\text{ + 4Cl}}^{\text{ - }}\rightleftharpoons {\text{CuCll}}^{\text{2 - }}$

The given reaction is not an acid-base reaction of Arrhenius because neither the ${\text{H}}^{\text{ + }}{\text{or OH}}^{\text{ - }}\text{.}$ are released by any of the reactants. It is also not a Bronsted-Lowry reaction because no proton transfer takes place. 

The given reaction is an acid-base reaction of Lewis because, as we can see, the   transferred its lone pair electron to the $C{u}^{2+}$ , resulting in the adduct $CuC{l}_4^{2-}$ . Therefore, the obtained result is a Lewis acid-base reaction.

Step 3: Finding all three reactions for Al(OH) 3  + 3HNO 3 ⇌ Al 3 +   + 3H 2 O + 3NO 3  - 

${\text{(b) Al(OH)}}_{\text{3}}{\text{ + 3HNO}}_{\text{3}}\rightleftharpoons {\text{Al}}^{\text{3 + }}{\text{ + 3H}}_{\text{2}}{\text{O + 3NO}}_{\text{3}}^{\text{ - }}$

Is it theThe given acid-base reaction is of Arrhenius because in the $\text{Al}(\text{OH}{)}_3$  the ${\text{OH}}^{-}$ and ${\text{HNO}}_3$  releases  ${\text{H}}^{+}.$ The reaction is also a Bronsted-Lowry reaction because, between the ${\text{H}}^{+}$ and $\text{Al}(\text{OH}{)}_3$ , there is a transfer of ${\text{HNO}}_3.$  It is also an acid-base reaction of Lewis because, as we can see, the lone pair of electron from the oxygen atom is contributed to the $\text{Al}(\text{OH}{)}_3$  by the ${\text{HNO}}_3$ .

Hence, the obtained result is Arrhenius, Bronsted-Lowry, and Lewis acid-base reactions.

Step 4: Finding all three reactions for N 2  + 3H 2 ⇌ 2NH 3

 ${\text{(c) N}}_{\text{2}}{\text{ + 3H}}_{\text{2}}\rightleftharpoons {\text{2NH}}_{\text{3}}$

Is it Arrhenius acid-base reaction?

No. because none of the reactants release  ${\text{H}}^{\text{ + }}{\text{or OH}}^{\text{ - }}\text{.}$

Is it the acid-base reaction of Bronsted-Lowry?

Yes. There is a ${\text{H}}^{+}$  transfer that takes place from  ${\text{H}}_{\text{2}}{\text{ to N}}_{\text{2}}$ to generate ${\text{NH}}_3$ .

Is it the acid-base reaction of Lewis?

Yes. As we can see, the nitrogen gives the $H_2$  its lone pair of electron.

Therefore, the obtained result is Bronsted-Lowry and Lewis acid base reaction.

Step 5: Finding all three reactions for  CN  -   + H 2 O ⇌ HCN + OH  - 

 ${\text{(d) CN}}^{\text{ - }}{\text{ + H}}_{\text{2}}\text{O}\rightleftharpoons {\text{HCN + OH}}^{\text{ - }}$

Is it the acid-base reaction of Arrhenius?

No, because even though the water was auto ionized to data-custom-editor="chemistry" ${\text{H}}^{\text{ + }},$  the data-custom-editor="chemistry" ${\text{OH}}^{\text{ - }}{\text{ and CN}}^{\text{ - }}$  did not dissociate to data-custom-editor="chemistry" $O{H}^{-}$ .

Is it the acid-base reaction of Bronsted-Lowry?

Yes. There was a transfer of data-custom-editor="chemistry" ${\text{H}}^{+}$  from the data-custom-editor="chemistry" ${\text{H}}_{\text{2}}\text{O to CN}$ .

Yes it the acid-base reaction of Lewis.

Yes. The lone pair electron from the nitrogen atom was donated by the data-custom-editor="chemistry" $C{N}^{-}$  to thedata-custom-editor="chemistry" ${\text{H}}_2\text{O}.$  , as shown.

Hence, the obtained result is Bronsted-Lowry and Lewis acid-base reaction.