Complete Ionic Equations: Videos & Practice Problems

Complete ionic equations represent aqueous compounds as their constituent ions, while solids, liquids, and gases remain intact. To derive a net ionic equation, spectator ions—those present in both reactants and products—are removed from the complete ionic equation. This process begins with a molecular equation, leading to the complete ionic equation, and finally to the net ionic equation. Understanding these relationships is crucial for analyzing chemical reactions, particularly in acid-base reactions and precipitation reactions, where identifying active ions is essential for predicting outcomes.

Complete Ionic Equations

In chemistry, understanding the transition from a molecular equation to a complete ionic equation is crucial for analyzing reactions in aqueous solutions. A molecular equation represents all reactants and products in their molecular forms, including solids, liquids, and gases, while a complete ionic equation breaks down only the aqueous compounds into their constituent ions.When dealing with aqueous compounds, it is essential to apply solubility rules to identify which substances will dissociate into ions. For instance, soluble salts will break apart into their respective ions, while solids, liquids, and gases remain intact in the equation. This distinction is vital for accurately representing the chemical reaction.To construct a complete ionic equation from a molecular equation, one must distribute the coefficients of each compound correctly. This means that if a compound has a coefficient greater than one, the number of ions produced must reflect that coefficient. For example, if a compound like sodium chloride (NaCl) is present with a coefficient of 2, it will dissociate into 2 Na⁺ ions and 2 Cl⁻ ions in the complete ionic equation.In summary, the complete ionic equation provides a clearer picture of the actual species involved in a reaction, particularly in aqueous solutions, by emphasizing the dissociation of soluble compounds while maintaining the integrity of solids, liquids, and gases. Understanding this process is essential for predicting the outcomes of chemical reactions and for further studies in reaction mechanisms and equilibrium.

Complete Ionic Equations Example 1

To convert a molecular equation into a complete ionic equation, it is essential to recognize which compounds can dissociate into ions. In this case, we have the reaction of 3 moles of calcium bromide (CaBr₂) aqueous with 2 moles of lithium phosphate (Li₃PO₄) aqueous, resulting in the formation of 6 moles of lithium bromide (LiBr) aqueous and 1 mole of calcium phosphate (Ca₃(PO₄)₂) solid.

Only the aqueous compounds will dissociate into their respective ions. Therefore, we will break down the calcium bromide, lithium phosphate, and lithium bromide into their ionic forms, while the calcium phosphate remains intact as a solid.

Starting with calcium bromide, the dissociation can be represented as follows:

3 CaBr₂ (aq) → 3 Ca²⁺ (aq) + 6 Br^- (aq)

Next, for lithium phosphate:

2 Li₃PO₄ (aq) → 6 Li⁺ (aq) + 2 PO₄^3- (aq)

Finally, lithium bromide dissociates as:

6 LiBr (aq) → 6 Li⁺ (aq) + 6 Br^- (aq)

Since calcium phosphate is a solid, it does not dissociate:

1 Ca₃(PO₄)₂ (s)

Combining all these components, the complete ionic equation is:

3 Ca²⁺ (aq) + 6 Br^- (aq) + 6 Li⁺ (aq) + 2 PO₄^3- (aq) → 6 Li⁺ (aq) + 6 Br^- (aq) + 1 Ca₃(PO₄)₂ (s)

In summary, when converting to a complete ionic equation, remember to only break apart aqueous compounds and distribute coefficients to the respective ions formed.

Complete Ionic Equations

A net ionic equation is a simplified representation of a chemical reaction that highlights the ions directly involved in the reaction while omitting the spectator ions. Spectator ions are those that appear unchanged on both sides of the equation, meaning they do not participate in the actual chemical change. To derive a net ionic equation, one must first start with the molecular equation, which represents the reactants and products in their molecular form.

From the molecular equation, the next step is to write the complete ionic equation. This equation breaks down all soluble ionic compounds into their respective ions, showing all species present in the reaction. Finally, by removing the spectator ions from the complete ionic equation, we arrive at the net ionic equation, which succinctly illustrates the essential chemical changes occurring during the reaction.

This process of transitioning from a molecular equation to a net ionic equation is crucial for understanding the specific interactions between ions in a solution, allowing for a clearer insight into the underlying chemistry of the reaction.

Complete Ionic Equations Example 2

When ammonium sulfate reacts with calcium chloride, the first step is to write the molecular equation. The reactants can be represented as ammonium sulfate (NH₄)₂SO₄ and calcium chloride CaCl₂. The balanced molecular equation for this reaction is:

(NH₄)₂SO₄ (aq) + CaCl₂ (aq) → 2 NH₄Cl (aq) + CaSO₄ (s)

In this equation, ammonium sulfate and calcium chloride are both soluble in water, while calcium sulfate precipitates as a solid due to its low solubility.

Next, we break down the soluble compounds into their ionic forms to create the complete ionic equation. Ammonium sulfate dissociates into 2 ammonium ions (2 NH₄⁺) and 1 sulfate ion (SO₄^2-), while calcium chloride dissociates into 1 calcium ion (Ca²⁺) and 2 chloride ions (2 Cl^-). The complete ionic equation is:

2 NH₄⁺ (aq) + SO₄^2- (aq) + Ca²⁺ (aq) + 2 Cl^- (aq) → 2 NH₄⁺ (aq) + 2 Cl^- (aq) + CaSO₄ (s)

In this equation, the ammonium ions and chloride ions are spectator ions, as they appear on both sides of the equation. To derive the net ionic equation, we remove these spectator ions, leaving us with:

SO₄^2- (aq) + Ca²⁺ (aq) → CaSO₄ (s)

This net ionic equation highlights the essential chemical change occurring in the reaction, which is the formation of solid calcium sulfate from the sulfate and calcium ions in solution. Understanding these steps is crucial for mastering the concepts of molecular, complete ionic, and net ionic equations in chemical reactions.

Provide the net ionic equation that occurs when the following aqueous compounds are mixed together: 
Copper (II) Bromide and Lithium Hydroxide

When mixing aqueous compounds such as copper(II) bromide and lithium hydroxide, we begin by identifying the ions present in each compound. Copper(II) bromide dissociates into copper ions (Cu²⁺) and bromide ions (Br^-), while lithium hydroxide dissociates into lithium ions (Li⁺) and hydroxide ions (OH^-).

The initial reaction can be represented as:

CuBr₂(aq) + 2 LiOH(aq) → 2 LiBr(aq) + Cu(OH)₂(s)

In this reaction, the lithium ions and bromide ions remain in solution, while copper(II) hydroxide precipitates as a solid. To derive the complete ionic equation, we break down the aqueous compounds into their constituent ions:

Cu²⁺(aq) + 2 Br^-(aq) + 2 Li⁺(aq) + 2 OH^-(aq) → 2 Li⁺(aq) + 2 Br^-(aq) + Cu(OH)₂(s)

Next, we identify and remove the spectator ions, which are ions that appear on both sides of the equation without undergoing any change. In this case, the lithium ions (Li⁺) and bromide ions (Br^-) are spectator ions. Thus, the net ionic equation focuses on the ions that participate in the formation of the precipitate:

Cu²⁺(aq) + 2 OH^-(aq) → Cu(OH)₂(s)

This net ionic equation illustrates the essential chemical change occurring in the reaction, highlighting the formation of solid copper(II) hydroxide from the aqueous copper and hydroxide ions.

Which of the following reagents could be used to separate the two anions from a solution containing magnesium nitrate and cesium hydroxide?

• A. NH₄CN
• B. NaCl
• C. KNO₃
• D. ZnBr₂
• E. CsBrO₃

Answer: (D)

Which of the following reagents could be used to separate the two cations from a solution containing Lead (IV) acetate and cesium permanganate?

• A. Sr(NO₃)₂
• B. TiC₂H₃O₂
• C. K₂S
• D. NaClO₄
• E. KNO₃

Answer: (C)

Here’s what students ask on this topic:

What is a complete ionic equation and how is it different from a molecular equation?

A complete ionic equation represents all of the ions present in an aqueous solution, showing aqueous compounds as their constituent ions. In contrast, a molecular equation shows the compounds in their complete, undissociated form. For example, the molecular equation for the reaction between sodium chloride and silver nitrate is:

${\mathrm{NaCl}}_{(aq)}+{\mathrm{AgNO}}_{(aq)}\to {\mathrm{NaNO}}_{(aq)}+{\mathrm{AgCl}}_{(s)}$

The complete ionic equation for the same reaction is:

${\mathrm{Na}}_{(aq)}+{\mathrm{Cl}}_{(aq)}+{\mathrm{Ag}}_{(aq)}+{\mathrm{NO}}_{(aq)}\to {\mathrm{Na}}_{(aq)}+{\mathrm{NO}}_{(aq)}+{\mathrm{AgCl}}_{(s)}$

How do you write a complete ionic equation from a molecular equation?

To write a complete ionic equation from a molecular equation, follow these steps:

1. Write the balanced molecular equation.
2. Identify the aqueous compounds and dissociate them into their constituent ions.
3. Keep solids, liquids, and gases in their molecular form.
4. Distribute the coefficients to each ion to ensure the correct number of ions is represented.

For example, for the reaction between barium chloride and sodium sulfate:

Molecular equation:

${\mathrm{BaCl}}_{(aq)}+{\mathrm{Na}}_{(aq)}\to {\mathrm{BaSO}}_{(s)}+{\mathrm{NaCl}}_{(aq)}$

Complete ionic equation:

${\mathrm{Ba}}_{(aq)}+{\mathrm{Cl}}_{(aq)}+{\mathrm{Na}}_{(aq)}+{\mathrm{SO}}_{(aq)}\to {\mathrm{BaSO}}_{(s)}+{\mathrm{Na}}_{(aq)}+{\mathrm{Cl}}_{(aq)}$

What are spectator ions and how do you identify them in a complete ionic equation?

Spectator ions are ions that appear on both the reactant and product sides of a complete ionic equation but do not participate in the actual chemical reaction. To identify them, follow these steps:

1. Write the complete ionic equation.
2. Compare the ions on both sides of the equation.
3. Identify the ions that remain unchanged in both the reactants and products.

For example, in the reaction between sodium chloride and silver nitrate:

Complete ionic equation:

${\mathrm{Na}}_{(aq)}+{\mathrm{Cl}}_{(aq)}+{\mathrm{Ag}}_{(aq)}+{\mathrm{NO}}_{(aq)}\to {\mathrm{Na}}_{(aq)}+{\mathrm{NO}}_{(aq)}+{\mathrm{AgCl}}_{(s)}$

Here, Na⁺ and NO₃⁻ are spectator ions because they appear unchanged on both sides of the equation.

How do you derive a net ionic equation from a complete ionic equation?

To derive a net ionic equation from a complete ionic equation, follow these steps:

1. Write the complete ionic equation.
2. Identify and remove the spectator ions, which are ions that appear unchanged on both sides of the equation.
3. Write the remaining ions that participate in the reaction.

For example, for the reaction between sodium chloride and silver nitrate:

Complete ionic equation:

${\mathrm{Na}}_{(aq)}+{\mathrm{Cl}}_{(aq)}+{\mathrm{Ag}}_{(aq)}+{\mathrm{NO}}_{(aq)}\to {\mathrm{Na}}_{(aq)}+{\mathrm{NO}}_{(aq)}+{\mathrm{AgCl}}_{(s)}$

Net ionic equation:

${\mathrm{Ag}}_{(aq)}+{\mathrm{Cl}}_{(aq)}\to {\mathrm{AgCl}}_{(s)}$

Why are complete ionic equations important in chemistry?

Complete ionic equations are important in chemistry because they provide a detailed view of the ions present in a reaction, helping to understand the behavior of substances in aqueous solutions. They are particularly useful in identifying the actual species involved in chemical reactions, such as in acid-base reactions and precipitation reactions. By showing the dissociation of aqueous compounds into ions, complete ionic equations help predict the formation of products, identify spectator ions, and derive net ionic equations. This detailed understanding is crucial for analyzing reaction mechanisms, predicting reaction outcomes, and solving problems in various fields of chemistry.