The Chemical Reaction Between Lead Nitrate and Sodium Sulfate: Formation of Lead Sulfate Precipitate

The interaction between lead nitrate, Pb(NO?)?, and sodium sulfate, Na?SO?, is a classic example of a double displacement reaction. This article delves into the details of the reaction, including chemical equations, observation, and thermodynamic properties.

Reaction Overview

Reactants: Lead nitrate and sodium sulfate.

Products: Lead sulfate (PbSO?), a white precipitate; and sodium nitrate (NaNO?), which remains in the solution as it is soluble in water.

Observation

The formation of a white precipitate of lead sulfate signifies that a reaction has taken place. This precipitate can be observed when an aqueous solution of lead nitrate is mixed with an aqueous solution of sodium sulfate.

Aqueous Solution Interaction

The reaction between these two salts can be represented by the following balanced chemical equation:

Pb(NO?)? (aq) Na?SO? (aq) → PbSO? (s) 2 NaNO? (aq)

Reaction Mechanism

This is a typical double displacement reaction where the cations and anions from the reactants are exchanged to form new compounds. In this case, the lead cation (Pb2?) from lead nitrate swaps places with the sodium cation (Na?) from sodium sulfate, forming lead sulfate and sodium nitrate.

Insolubility of Lead Sulfate

Lead sulfate is poorly soluble in water, making it a solid precipitate. The equation for the formation of lead sulfate can be simplified as:

Pb2? SO?2? → PbSO? (s)

Thermodynamic Analysis

The thermodynamics of the reaction provide further insight into its behavior:

Change in Free Energy (ΔG)

ΔG??°C -12.7 kJ - A negative value indicates that the reaction is spontaneous under standard conditions.

Change in Enthalpy (ΔH)

ΔH??°C -10.7 kJ - A negative value suggests that the reaction is exothermic, releasing energy.

Chemical Quantities and Limiting Reactant

To demonstrate the reaction, a sample of 1.05 grams of lead(II) nitrate is mixed with 122 mL of a 0.101 M sodium sulfate solution. In this case, the limiting reactant is Pb(NO?)?.

Reaction Happens Due to Solubility

The precipitate formation is a direct result of the low solubility of lead sulfate in water. The ion exchange can be summarized as:

Pb(NO?)? (aq) Na?SO? (aq) → PbSO? (s) 2 NaNO? (aq)

Lead sulfate and sodium nitrate are more thermodynamically stable in this configuration compared to the individual starting compounds, leading to the precipitation reaction.

Conclusion

The interaction between lead nitrate and sodium sulfate is a textbook example of a double displacement reaction, highlighting the principles of solubility product and reaction spontaneity. The precipitate formation of lead sulfate not only serves as a practical demonstration of chemical reactions but also provides valuable insights into the predictive power of thermodynamics in chemical processes.