Problem 132 - Chemistry The Molecular Science

Question

Students were asked to prepare nickel sulfate by reacting a nickel compound with a sulfate compound in water and then evaporating the water. Three students chose these pairs of reactants: $$\begin{array}{ll} \hline \text { Student } 1 & \mathrm{Ni}(\mathrm{OH})_{2} \text { and } \mathrm{H}_{2} \mathrm{SO}_{4} \\ \text { Student } 2 & \mathrm{Ni}\left(\mathrm{NO}_{3}\right)_{2} \text { and } \mathrm{Na}_{2} \mathrm{SO}_{4} \\ \text { Student } 3 & \mathrm{NiCO}_{3} \text { and } \mathrm{H}_{2} \mathrm{SO}_{4} \\ \hline\end{array}$$ Comment on each student's choice of reactants and how successful you think each student will be at preparing nickel sulfate by the procedure indicated.

Step-by-Step Solution

Answer

Students 1 and 3 will successfully produce nickel sulfate; Student 2 may face separation issues.

Step 1: Understand the Procedure

The task is to prepare nickel sulfate (\(\text{NiSO}_4\)) by reacting a nickel compound and a sulfate compound in water, then evaporating the water.

Step 2: Evaluate Student 1's Reactants

Student 1 uses nickel hydroxide \(\text{Ni(OH)}_2\) and sulfuric acid \(\text{H}_2\text{SO}_4\). The reaction between these is: \[ \text{Ni(OH)}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + 2\text{H}_2\text{O} \] This reaction will successfully produce nickel sulfate and water. Evaporating the water will leave nickel sulfate, indicating this choice is appropriate.

Step 3: Evaluate Student 2's Reactants

Student 2 uses nickel nitrate \(\text{Ni(NO}_3)_2\) and sodium sulfate \(\text{Na}_2\text{SO}_4\). The possible reaction is: \[ \text{Ni(NO}_3)_2 + \text{Na}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + 2\text{NaNO}_3 \] A precipitate or a need for separation of products might arise, making isolation of pure nickel sulfate difficult though theoretically possible.

Step 4: Evaluate Student 3's Reactants

Student 3 uses nickel carbonate \(\text{NiCO}_3\) and sulfuric acid \(\text{H}_2\text{SO}_4\). The reaction is: \[ \text{NiCO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + \text{H}_2\text{O} + \text{CO}_2 \] This reaction produces nickel sulfate, water, and carbon dioxide gas which will escape, leaving nickel sulfate upon evaporation. This choice is suitable.

Step 5: Conclusion on Success Rate

Student 1 and Student 3 will successfully produce nickel sulfate, with Student 1 having a straightforward outcome. Student 2 may face challenges due to the formation of sodium nitrate, which might complicate the separation of nickel sulfate.

Key Concepts

Nickel Sulfate Preparation

Nickel sulfate preparation involves reacting a nickel-containing compound with a sulfate-producing compound, followed by the evaporation of water to obtain nickel sulfate. This process is an elementary example of a chemical reaction involving solution chemistry and evaporation techniques.
Nickel sulfate (\(\text{NiSO}_4\)) can be synthesized in various ways based on the reactants chosen. In this context, selecting appropriate reactants is crucial for a successful reaction. The reactant pair must be capable of undergoing a chemical reaction that produces the desired nickel sulfate as the primary product.
Common methods include reacting nickel hydroxide or nickel carbonate with dilute acid, like sulfuric acid. Upon evaporation, nickel sulfate crystallizes from the solution. The reaction is considered complete when no further visible changes occur, and the reactant quantities match the stoichiometric requirements of the chemical equation.

Reactant Evaluation

Evaluating reactants involves understanding whether the selected chemicals will effectively produce the desired product. In the students' exercise, we examine the suitability of their choices based on chemical stoichiometry and reaction by-products.- **Student 1's Reactants:** Nickel hydroxide (\(\text{Ni(OH)}_2\)) and sulfuric acid (\(\text{H}_2\text{SO}_4\)) react to yield nickel sulfate and water. This choice is optimal because it leads directly to a pure product without side complications.
The balanced reaction is straightforward, giving a clear pathway to nickel sulfate:\[\text{Ni(OH)}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + 2\text{H}_2\text{O}\]- **Student 2's Reactants:** Nickel nitrate (\(\text{Ni(NO}_3)_2\)) and sodium sulfate (\(\text{Na}_2\text{SO}_4\)) can theoretically produce nickel sulfate. However, this reaction also forms sodium nitrate, which poses a separation challenge. Achieving pure nickel sulfate requires additional purification steps, complicating the process.- **Student 3's Reactants:** Nickel carbonate (\(\text{NiCO}_3\)) and sulfuric acid react well together: \[\text{NiCO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + \text{H}_2\text{O} + \text{CO}_2\] This reaction results in nickel sulfate, water, and carbon dioxide gas. The evolving gas simplifies the purification process by naturally escaping, leaving the solid product behind after evaporation.

Reaction Equations

Chemical reaction equations represent the transformation of reactants into products, detailing all substances involved. They are essential for predicting the outcome of a chemical process and understanding stoichiometry.
In the preparation of nickel sulfate, three different chemical reactions are examined based on various nickel compounds:- For Student 1:\[\text{Ni(OH)}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + 2\text{H}_2\text{O}\]The simplicity of this reaction allows a direct synthesis of nickel sulfate without side products.- For Student 2:\[\text{Ni(NO}_3)_2 + \text{Na}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + 2\text{NaNO}_3\]Here, sodium nitrate is also formed, complicating the extraction of pure nickel sulfate due to the extra product formed, which remains in solution if not managed.- For Student 3:\[\text{NiCO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + \text{H}_2\text{O} + \text{CO}_2\]Their equation allows the escape of carbon dioxide gas, facilitating the purification by simplifying the mixture.