Chapter U6.2, Problem 6E

(a)

Interpretation Introduction

Interpretation: The colour of the solution on adding chloride is to be explained.

Concept Introduction : A reversible process in one that can proceed in both forward and the reverse direction. Many physical and chemical processes are reversible given the appropriate conditions.

Answer to Problem 6E

Addition of chloride makes the solution yellow.

Explanation of Solution

Reversible reactions do not go to completion. The forward and the back reaction occur in the system at the same time. This means that reactant and product both present at the same time.

The given net ionic equation is as follows:

  $\begin{array}{l}{\text{Ni(H}}_{\text{2}}\text{O}{)}_6{}^{2+}(aq)+4{\text{Cl}}^{-}(aq)\rightleftharpoons {\text{NiCl}}_{\text{4}}{}^{2-}(aq)+6{\text{H}}_{\text{2}}\text{O}\text{(}l\text{)}\\ \text{Green}\text{Yellow}\end{array}$

Addition of chloride to the sample of green solution, creates ${\text{NiCl}}_{\text{4}}{}^{2-}$ ions, which turned the test solution yellow. In this reaction, chloride ions replace the water molecules organized around the metal cation. If enough ions are added, the solution becomes yellow.

(b)

Interpretation Introduction

Interpretation: The colour of the solution on adding water is to be explained.

Concept Introduction : A reversible process in one that can proceed in both forward and the reverse direction. Many physical and chemical processes are reversible given the appropriate conditions.

Answer to Problem 6E

Addition of water to the solution makes the solution green.

Explanation of Solution

The given net ionic equation is as follows:

  $\begin{array}{l}{\text{Ni(H}}_{\text{2}}\text{O}{)}_6{}^{2+}(aq)+4{\text{Cl}}^{-}(aq)\rightleftharpoons {\text{NiCl}}_{\text{4}}{}^{2-}(aq)+6{\text{H}}_{\text{2}}\text{O}\text{(}l\text{)}\\ \text{Green}\text{Yellow}\end{array}$

To reverse the reaction, more water should be added to the system. This will result the formation of original reactant, that is, hexaaquonickel cation which is green in colour.

(c)

Interpretation Introduction

Interpretation: The ion which is not included in the equation is to be identified.

Concept Introduction : Net ionic equation is the chemical equation in which only the ions participate in the reaction are shown. In complete ionic equation, all the ions (participating or non-participating) are shown. In net ionic equation, spectator ions are cancelled.

Answer to Problem 6E

The ion which is not included in the equation is calcium ion.

Explanation of Solution

Given that the reaction takes place between aqueous hexaaquonickel cations and aqueous calcium chloride. But the given net ionic equation is,

  $\begin{array}{l}{\text{Ni(H}}_{\text{2}}\text{O}{)}_6{}^{2+}(aq)+4{\text{Cl}}^{-}(aq)\rightleftharpoons {\text{NiCl}}_{\text{4}}{}^{2-}(aq)+6{\text{H}}_{\text{2}}\text{O}\text{(}l\text{)}\\ \text{Green}\text{Yellow}\end{array}$

In the above equation, calcium ions are missing. So, the missing ion is calcium ion.

(d)

Interpretation Introduction

Interpretation: The indication of double arrow of the reaction is to be explained.

Concept Introduction: A reversible process in one that can proceed in both forward and the reverse direction. Many physical and chemical processes are reversible given the appropriate conditions.

Answer to Problem 6E

In a chemical equation, double arrow is used to show the reversible nature of reaction.

Explanation of Solution

The given net ionic equation is as follows:

  $\begin{array}{l}{\text{Ni(H}}_{\text{2}}\text{O}{)}_6{}^{2+}(aq)+4{\text{Cl}}^{-}(aq)\rightleftharpoons {\text{NiCl}}_{\text{4}}{}^{2-}(aq)+6{\text{H}}_{\text{2}}\text{O}\text{(}l\text{)}\\ \text{Green}\text{Yellow}\end{array}$

Addition of chloride to the sample of green solution, creates ${\text{NiCl}}_{\text{4}}{}^{2-}$ ions, which turned the test solution yellow. In this reaction, chloride ions replace the water molecules organized around the metal cation. If enough ions are added, the solution becomes yellow.

To reverse the reaction, more water should be added to the system. This will result the formation of original reactant, that is, hexaaquonickel cation which is green in colour. So, the reaction is reversible in nature and this reversibility is indicated by the double arrow.