Chapter 11, Problem 57A

(a)

Interpretation Introduction

Interpretation:

The formula of the yellow precipitate needs to be determined which is formed when aqueous solutions of sodium sulfide and cadmium nitrate were mixed in a beaker.

Concept Introduction:

A suspended solid particle that settles at the bottom of the solution when a chemical reaction occurs in a liquid solution is called a precipitate.

Answer to Problem 57A

The formula for yellow precipitate is $\text{CdS}\left(\text{s}\right)$ .

Explanation of Solution

A yellow precipitate is formed by mixing sodium sulfide and calcium nitrate since in the tube sodium sulfide and cadmium nitrate are mixed.

The balanced chemical equation is as:

  ${\text{Na}}_{\text{2}}\text{S}\left(\text{aq}\right)\text{+ Cd}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)\to \text{CdS}\left(\text{s}\right){\text{+ 2NaNO}}_{\text{3}}\left(\text{aq}\right)$

Hence the formula for yellow precipitate is $\text{CdS}\left(\text{s}\right)$ .

(b)

Interpretation Introduction

Interpretation:

The spectator ions need to be identified when aqueous solutions of sodium sulfide and cadmium nitrate were mixed in a beaker.

Concept Introduction:

An ion that exists as a reactant and a product in a chemical equation is called a spectator ion.

Answer to Problem 57A

The spectator ions are ${\text{Na}}^{+}\left(\text{aq}\right)$ and ${\left({\text{NO}}_3\right)}^{-}\left(\text{aq}\right)$ .

Explanation of Solution

The given reaction is as follows:

  ${\text{Na}}_{\text{2}}\text{S}\left(\text{aq}\right)\text{+ Cd}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)\to \text{CdS}\left(\text{s}\right){\text{+ 2NaNO}}_{\text{3}}\left(\text{aq}\right)$

For the above reaction, the ionic equation can be written as follows:

  ${\text{2Na}}^{+}\left(\text{aq}\right){\text{+S}}^{2-}\left(\text{aq}\right){\text{+ Cd}}^{2+}\left(aq\right)+2{\text{NO}}_{\text{3}}{}^{-}\left(\text{aq}\right)\to \text{CdS}\left(\text{s}\right){\text{+ 2Na}}^{+}{\text{+2NO}}_{\text{3}}{}^{-}\left(\text{aq}\right)$

Since, ${\text{Na}}^{+}\left(\text{aq}\right)$ and ${\left({\text{NO}}_3\right)}^{-}\left(\text{aq}\right)$ are on both sides of the ionic equation, thus,

  ${\text{Na}}^{+}\left(\text{aq}\right)$ and ${\left({\text{NO}}_3\right)}^{-}\left(\text{aq}\right)$ ions are spectator ions.

(c)

Interpretation Introduction

Interpretation:

The balanced net ionic equation needs to be determined for the reaction when aqueous solutions of sodium sulfide and cadmium nitrate were mixed in a beaker.

Concept Introduction:

A net ionic equation is an ionic equation in which spectator ions are not written.

Answer to Problem 57A

The balanced net ionic equation is ${\text{Cd}}^{\text{2+}}\left(\text{aq}\right){\text{+ S}}^{\text{2-}}\left(\text{aq}\right)\to \text{CdS}\left(\text{s}\right)$ .

Explanation of Solution

Chemical symbols and formulas are used for representing a chemical reaction where reactants are written on the left side and chemical products are written on the right side.

The chemical equation is balanced by making the number and types of atoms on the left and right sides of the equation as same.

The ionic equation is as follows:

  ${\text{2Na}}^{+}\left(\text{aq}\right){\text{+S}}^{2-}\left(\text{aq}\right){\text{+ Cd}}^{2+}\left(aq\right)+2{\text{NO}}_{\text{3}}{}^{-}\left(\text{aq}\right)\to \text{CdS}\left(\text{s}\right){\text{+ 2Na}}^{+}{\text{+2NO}}_{\text{3}}{}^{-}\left(\text{aq}\right)$

Here, ${\text{Na}}^{+}\left(\text{aq}\right)$ and ${\left({\text{NO}}_3\right)}^{-}\left(\text{aq}\right)$ ions are spectator ions; thus, the net ionic equation can be represented as follows:

  ${\text{Cd}}^{\text{2+}}\left(\text{aq}\right){\text{+ S}}^{\text{2-}}\left(\text{aq}\right)\to \text{CdS}\left(\text{s}\right)$