Question

Write ionic and net ionic equations for the following reactions: (a) \(\mathrm{AgNO}_{3}(a q)+\mathrm{Na}_{2} \mathrm{SO}_{4}(a q) \longrightarrow\) (b) \(\mathrm{BaCl}_{2}(a q)+\mathrm{ZnSO}_{4}(a q) \longrightarrow\) (c) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(a q)+\mathrm{CaCl}_{2}(a q) \longrightarrow\)

Short answer

\n(a) \(\mathrm{Ag}^{+}(a q) + \mathrm{SO}_{4}^{2-}(a q) \longrightarrow \mathrm{Ag}_{2}\mathrm{SO}_{4}(s)\)\n(b) \(\mathrm{Ba}^{2+}(a q) + \mathrm{SO}_{4}^{2-}(a q) \longrightarrow \mathrm{BaSO}_{4}(s)\)\n(c) \(\mathrm{CO}_{3}^{2-}(a q) + \mathrm{Ca}^{2+}(a q) \longrightarrow \mathrm{CaCO}_{3}(s)\)

Step-by-step solution

Write down the molecular equations

Remembering the solubility rules, figure out the products of the reactions and balance the equations. They will be:\n(a) \(\mathrm{AgNO}_{3}(a q)+\mathrm{Na}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Ag}_{2}\mathrm{SO}_{4}(s) + 2\mathrm{NaNO}_{3}(a q)\)\n(b) \(\mathrm{BaCl}_{2}(a q)+\mathrm{ZnSO}_{4}(a q) \longrightarrow \mathrm{BaSO}_{4}(s) + \mathrm{ZnCl}_{2}(a q)\)\n(c) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(a q)+\mathrm{CaCl}_{2}(a q) \longrightarrow \mathrm{CaCO}_{3}(s) + 2\mathrm{NH}_{4}\mathrm{Cl}(a q)\)

Write down the complete ionic equations

Split all soluble (aq) compounds into their ions (this is the complete ionic equation)\n(a) \(\mathrm{Ag}^{+}(a q) + \mathrm{NO}_{3}^{-}(a q) + 2\mathrm{Na}^{+}(a q) + \mathrm{SO}_{4}^{2-}(a q) \longrightarrow \mathrm{Ag}_{2}\mathrm{SO}_{4}(s) + 2\mathrm{Na}^{+}(a q) + 2\mathrm{NO}_{3}^{-}(a q)\)\n(b) \(\mathrm{Ba}^{2+}(a q) + 2\mathrm{Cl}^{-}(a q) + \mathrm{Zn}^{2+}(a q) + \mathrm{SO}_{4}^{2-}(a q) \longrightarrow \mathrm{BaSO}_{4}(s) + \mathrm{Zn}^{2+}(a q) + 2\mathrm{Cl}^{-}(a q)\)\n(c) \(\mathrm{NH}_{4}^{+}(a q) + \mathrm{CO}_{3}^{2-}(a q) + \mathrm{Ca}^{2+}(a q) + 2\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{CaCO}_{3}(s) + 2\mathrm{NH}_{4}^{+}(a q) + 2\mathrm{Cl}^{-}(a q)\)

Write down the net ionic equations

Cancel out the common ions on both sides to get the net ionic equation\n(a) \(\mathrm{Ag}^{+}(a q) + \mathrm{SO}_{4}^{2-}(a q) \longrightarrow \mathrm{Ag}_{2}\mathrm{SO}_{4}(s)\)\n(b) \(\mathrm{Ba}^{2+}(a q) + \mathrm{SO}_{4}^{2-}(a q) \longrightarrow \mathrm{BaSO}_{4}(s)\)\n(c) \(\mathrm{CO}_{3}^{2-}(a q) + \mathrm{Ca}^{2+}(a q) \longrightarrow \mathrm{CaCO}_{3}(s)\)

Key concepts

Net Ionic Equation

When writing a chemical reaction, understanding the net ionic equation is key to grasping what's happening at the molecular level. Net ionic equations focus only on the components directly involved in the chemical change, cutting out the spectator ions that do not participate in the reaction. To arrive at a net ionic equation, start by writing the complete ionic equation. This includes all the ions present in the reaction. From there, identify and remove the spectator ions, which appear on both sides of the equation. What's left behind is the net ionic equation.

• Start with the balanced molecular equation for the reaction.
• Split the soluble compounds into individual ions to form the complete ionic equation.
• Identify ions that do not change during the reaction; these are the spectator ions.
• Eliminate the spectator ions to reveal the net ionic equation.

The net ionic equation provides a clearer picture of the actual chemical change occurring and is helpful in various applications, such as predicting the formation of a precipitate or understanding redox reactions.

Solubility Rules

Solubility rules are guidelines that help predict the solubility of compounds in water. These rules are crucial for determining which compounds will dissociate into ions and participate in chemical reactions. Knowing the solubility is essential when writing ionic and net ionic equations because it influences which compounds appear in their ionic forms.

• Compounds containing alkali metal ions (like Li, Na) and ammonium ion (NH₄⁺) are generally soluble.
• Nitrates (NO₃⁻), acetates (CH₃COO⁻), and perchlorates (ClO₄⁻) are soluble.
• Most chlorides, bromides, and iodides are soluble, except those of silver, lead, and mercury.
• Sulfates (SO₄²⁻) are generally soluble, except for those of barium, strontium, lead, and calcium.
• Carbonates (CO₃²⁻), phosphates (PO₄³⁻), sulfides, and hydroxides are usually insoluble; however, compounds with alkali metals and ammonium are exceptions.

By applying these solubility rules, you can predict which products in a reaction will precipitate, thus identifying the substances involved in the net ionic equation.

Molecular Equation

A molecular equation shows the chemical formulas of substances that are involved in the reaction as compounds, rather than separating them into ions. This offers a complete picture of the chemical reaction as it might occur. The molecular equation is the starting point before breaking it down into ionic components.

• List all reactants and products in their standard chemical form, not as individual ions.
• Use coefficients to balance the chemical equation, ensuring that the number of atoms of each element is the same on both sides.

From the molecular equation, chemists can assess the overall reaction and its feasibility under given conditions. While not as detailed in terms of ionic participation as the net ionic equation, the molecular equation remains an essential step in deriving the more detailed ionic forms.