Question

Potassium sulfate solution reacts with barium bromide solution to produce a precipitate of barium sulfate and a solution of potassium bromide. Write the molecular equation for this reaction. Then write the corresponding net ionic equation.

Short answer

Net ionic equation: \(Ba^{2+} (aq) + SO_4^{2-} (aq) \rightarrow BaSO_4 (s)\).

Step-by-step solution

Identify the reactants and products

The reactants in the chemical reaction are potassium sulfate (\(K_2SO_4\)) and barium bromide (\(BaBr_2\)). The products are barium sulfate (\(BaSO_4\)) precipitate and potassium bromide (\(KBr\)) solution.

Write the balanced molecular equation

The balanced molecular equation for the reaction is:\[K_2SO_4 (aq) + BaBr_2 (aq) \rightarrow BaSO_4 (s) + 2KBr (aq)\]This equation follows the law of conservation of mass, ensuring the number of each type of atom is the same on both sides of the equation.

Write the total ionic equation

The total ionic equation shows all the ions separately as they exist in solution:\[2K^+ (aq) + SO_4^{2-} (aq) + Ba^{2+} (aq) + 2Br^- (aq) \rightarrow BaSO_4 (s) + 2K^+ (aq) + 2Br^- (aq)\]In this equation, the potassium and bromide ions remain aqueous and do not participate in forming the precipitate.

Identify and remove spectator ions

Spectator ions are those that appear unchanged on both sides of the equation. In this case, \(K^+\) and \(Br^-\) are spectator ions because they do not participate in the formation of the precipitate.

Write the net ionic equation

The net ionic equation only includes the ions and compounds that undergo a chemical change during the reaction:\[Ba^{2+} (aq) + SO_4^{2-} (aq) \rightarrow BaSO_4 (s)\]This equation shows that barium ions and sulfate ions combine to form the solid barium sulfate precipitate.

Key concepts

Molecular Equation

A molecular equation provides a detailed snapshot of a chemical reaction, showing all reactants and products in their undissociated molecular forms. It serves as a starting point for understanding the complete chemical process. For example, when potassium sulfate reacts with barium bromide, the molecular equation is:

• \[ K_2SO_4 (aq) + BaBr_2 (aq) \rightarrow BaSO_4 (s) + 2KBr (aq) \]

Here is what each part represents:

• The formula \( K_2SO_4 (aq) \) stands for potassium sulfate dissolved in water.
• \( BaBr_2 (aq) \) is barium bromide in aqueous form.
• \( BaSO_4 (s) \) denotes barium sulfate, a solid precipitate.
• \( 2KBr (aq) \) is potassium bromide remaining in solution.

The balance of the equation ensures that there is the same number of each element's atoms before and after the reaction. This satisfies the law of conservation of mass, which is crucial for all chemical equations.

Spectator Ions

In chemical reactions like the precipitation of barium sulfate from potassium sulfate and barium bromide, you'll often find ions that appear on both sides of the equation unchanged. These are known as spectator ions. They are present in the solution but do not participate in forming the precipitate. In our reaction:

• Potassium \( K^+ \) ions start in solution and remain there.
• Similarly, bromide \( Br^- \) ions are present before and after the reaction.

These ions are considered 'spectators' as they do not take part in the actual precipitation. Removing these ions from the equation results in the net ionic equation, which shows only the ions that undergo chemical change. Understanding spectator ions helps to simplify and focus on the essential components of a chemical reaction.

Precipitation Reaction

A precipitation reaction offers a fascinating look into how insoluble solids can emerge from solutions. In this type of reaction, an insoluble solid forms, known as the precipitate, which emerges from the clear solution. When potassium sulfate reacts with barium bromide:

• Barium ions \( Ba^{2+} \) and sulfate ions \( SO_4^{2-} \) interact to form barium sulfate \( BaSO_4 \).
• This new compound \( BaSO_4 \) appears as a solid precipitate, because it is not soluble in water.

The formation of a precipitate is crucial as it changes the solution's composition, leading to potential applications in purification or separation processes. The net ionic equation for this reaction:

• \[ Ba^{2+} (aq) + SO_4^{2-} (aq) \rightarrow BaSO_4 (s) \]

encapsulates the essence of the precipitation reaction. This simplified depiction focuses solely on the ions that create the solid, omitting spectator ions to highlight the chemical change.