Question

II. Ionic Equations

8. Write the complete ionic and net ionic equations for the reaction below:
2 AgNO3(aq) + CaCl2(aq) → 2 AgCl + Ca(NO3)2
Complete ionic:
Net ionic:

Answer 1

Complete ionic:
`\begin{aligned}& \rm 2\, Ag^(+)\, (aq) + 2\, {NO_3}^(-) \, (aq) + Ca^(2+)\, (aq) + 2\, Cl^(-)\, (aq) \\ & \rm \to 2\, AgCl\, (s) + Ca^(2+)\, (aq) + 2\, {NO_3}^(-)\, (aq)\end{aligned}`.

Net ionic:
`\begin{aligned}& \rm Ag^(+)\, (aq) + Cl^(-)\, (aq) \to AgCl\, (s)\end{aligned}`.

Step-by-step explanation:

Start by identifying species that exist as ions. In general, such species include:

• Soluble salts.
• Strong acids and strong bases.

All four species in this particular question are salts. However, only three of them are generally soluble in water:
`\rm AgNO_3`,
`\rm CaCl_2`, and
`\rm Ca(NO_3)_2`. These three salts will exist as ions:

• Each
  `\rm AgNO_3\, (aq)` formula unit will exist as one
  `\rm Ag^(+)` ion and one
  `\rm {NO_3}^(-)` ion.
• Each
  `\rm CaCl_2` formula unit will exist as one
  `\rm Ca^(2+)` ion and two
  `\rm Cl^(-)` ions (note the subscript in the formula
  `\rm CaCl_2\!`.)
• Each
  `\rm Ca(NO_3)_2` formula unit will exist as one
  `\rm Ca^(2+)` and two
  `\rm {NO_3}^(-)` ions.

On the other hand,
`\rm AgCl` is generally insoluble in water. This salt will not form ions.

Rewrite the original chemical equation to get the corresponding ionic equation. In this question, rewrite
`\rm AgNO_3`,
`\rm CaCl_2`, and
`\rm Ca(NO_3)_2` (three soluble salts) as the corresponding ions.

Pay attention to the coefficient of each species. For example, indeed each
`\rm AgNO_3\, (aq)` formula unit will exist as only one
`\rm Ag^(+)` ion and one
`\rm {NO_3}^(-)` ion. However, because the coefficient of
`\rm AgNO_3\, (aq)\!` in the original equation is two,
`\!\rm AgNO_3\, (aq)` alone should correspond to two
`\rm Ag^(+)\!` ions and two
`\rm {NO_3}^(-)\!` ions.

Do not rewrite the salt
`\rm AgCl` because it is insoluble.

`\begin{aligned}& \rm 2\, Ag^(+)\, (aq) + 2\, {NO_3}^(-) \, (aq) + Ca^(2+)\, (aq) + 2\, Cl^(-)\, (aq) \\ & \rm \to 2\, AgCl\, (s) + Ca^(2+)\, (aq) + 2\, {NO_3}^(-)\, (aq)\end{aligned}`.

Eliminate ions that are present on both sides of this ionic equation. In this question, such ions include one unit of
`\rm Ca^(2+)` and two units of
`\rm {NO_3}^(-)`. Doing so will give:

`\begin{aligned}& \rm 2\, Ag^(+)\, (aq) + 2\, Cl^(-)\, (aq) \to 2\, AgCl\, (s)\end{aligned}`.

Simplify the coefficients:

`\begin{aligned}& \rm Ag^(+)\, (aq) + Cl^(-)\, (aq) \to AgCl\, (s)\end{aligned}`.