Chapter 5, Problem 102QP

(a)

Interpretation Introduction

Interpretation:

A balanced net ionic equation for the given reaction is to be written with physical state of each substance.

Explanation of Solution

Except for chromium (III) hydroxide (Cr(OH)3), all other substances in the given reaction are electrolytes. The molecular equation of the given reaction with the physical state of each substance is as follows:

${\text{Cr}}_{\text{2}}{{\text{(SO}}_4\text{)}}_3(aq)+6\text{KOH}(aq)\to 2{\text{Cr(OH)}}_3(s)+3{\text{K}}_{\text{2}}{\text{SO}}_4(aq)$

In an ionic equation, the electrolytes are written as separated ions. The ionic equation of the given reaction is as follows:

$2{\text{Cr}}^{3+}(aq)+3{\text{SO}}_4^{2-}(aq)+6{\text{K}}^{+}(aq)+6{\text{OH}}^{-}(aq)\to 2{\text{Cr(OH)}}_3(s)+6{\text{K}}^{+}(aq)+3{\text{SO}}_4^{2-}(aq)$

Potassium ion (Na+) and sulfate ion are spectator ions in the given reaction and are removed to get the net ionic equation. The net ionic equation is as follows:

$2{\text{Cr}}^{3+}(aq)+6{\text{OH}}^{-}(aq)\to 2{\text{Cr(OH)}}_3(s)$

Both the chromium ion and hydroxyl ion are balanced by multiplying the appropriate number. The balanced net ionic equation is as follows:

${\text{Cr}}^{3+}(aq)+3{\text{OH}}^{-}(aq)\to {\text{Cr(OH)}}_3(s)$

(b)

Interpretation Introduction

Interpretation:

A balanced net ionic equation for the given reaction is to be written with physical state of each substance.

Explanation of Solution

Lead (II) chloride (PbCl2) and lead (II) chromate (PbCrO4) are non-electrolytes whereas potassium chloride (KCl) and potassium chromate (K2CrO4) are electrolytes. The molecular equation with the physical state of each substance is as follows:

${\text{K}}_{\text{2}}{\text{CrO}}_4(aq)+{\text{PbCl}}_{\text{2}}(s)\to \text{KCl}(aq)+{\text{PbCrO}}_4(s)$

The ionic equation of the above reaction is as follows:

$2{\text{K}}^{+}(aq)+{\text{CrO}}_4^{2-}(aq)+{\text{PbCl}}_{\text{2}}(s)\to {\text{K}}^{+}(aq)+{\text{Cl}}^{-}(aq)+{\text{PbCrO}}_4(s)$

As potassium ion is spectator ion, the net ionic equation is as follows:

${\text{CrO}}_4^{2-}(aq)+{\text{PbCl}}_{\text{2}}(s)\to {\text{Cl}}^{-}(aq)+{\text{PbCrO}}_4(s)$

The above equation is balanced by putting coefficient 2 in front of chloride ion. The balanced net ionic equation is as follows:

${\text{CrO}}_4^{2-}(aq)+{\text{PbCl}}_{\text{2}}(s)\to 2{\text{Cl}}^{-}(aq)+{\text{PbCrO}}_4(s)$

(c)

Interpretation Introduction

Interpretation:

A balanced net ionic equation for the given reaction is to be written with physical state of each substance.

Explanation of Solution

Except for sulfur dioxide (SO2) and water (H2O), all other substances in the given reaction areelectrolytes. The molecular equation for the given reaction is as follows:

${\text{Na}}_{\text{2}}{\text{SO}}_3(aq)+{\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}(aq)\to {\text{Na}}_2{\text{SO}}_4(aq)+{\text{H}}_{\text{2}}\text{O}(l)+{\text{SO}}_2(g)$

The ionic equation is as follows:

$2{\text{Na}}^{+}(aq)+{\text{SO}}_3^{2-}(aq)+2{\text{H}}^{+}(aq)+{\text{SO}}_4^{2-}(aq)\to 2{\text{Na}}^{+}(aq)+{\text{SO}}_4^{2-}(aq)+{\text{H}}_{\text{2}}\text{O}(l)+{\text{SO}}_2(g)$

As sodium and sulfate ion are spectator ions, the net ionic equation is as follows:

${\text{SO}}_3^{2-}(aq)+2{\text{H}}^{+}(aq)\to {\text{H}}_{\text{2}}\text{O}(l)+{\text{SO}}_2(g)$

The above equation is already balanced.