Question

Apply Describe the reaction of aqueous solutions of sodium sulfide and copper(II) sulfate, producing the precipitate copper(II) sulfide.

Short answer

The reaction between aqueous sodium sulfide (Na_2S) and copper(II) sulfate (CuSO_4) is a double replacement reaction that produces a solid precipitate of copper(II) sulfide (CuS) and an aqueous solution of sodium sulfate (Na_2SO_4). The balanced chemical equation for this reaction is: Na_2S (aq) + CuSO_4 (aq) → CuS (s) + Na_2SO_4 (aq)

Step-by-step solution

Write the chemical formulas of the reactants and products

The reactants are aqueous sodium sulfide and copper(II) sulfate. - Sodium sulfide: Na_2S (aq) - Copper(II) sulfate: CuSO_4 (aq) The products are copper(II) sulfide (the precipitate) and sodium sulfate. - Copper(II) sulfide: CuS (s) - Sodium sulfate: Na_2SO_4 (aq)

Write the balanced chemical equation

Now, we will write the balanced chemical equation: Na_2S (aq) + CuSO_4 (aq) → CuS (s) + Na_2SO_4 (aq) This equation is already balanced since there are 2 sodium (Na), 1 sulfur (S), 1 copper (Cu), and 4 oxygen (O) atoms on both sides of the equation.

Describe the reaction

The reaction between aqueous sodium sulfide (Na_2S) and copper(II) sulfate (CuSO_4) forms a solid precipitate of copper(II) sulfide (CuS) and an aqueous solution of sodium sulfate (Na_2SO_4). This is a double replacement reaction where the two reacting compounds exchange their respective ions, resulting in the production of a precipitate and a soluble compound. The balanced chemical equation for the reaction is: Na_2S (aq) + CuSO_4 (aq) → CuS (s) + Na_2SO_4 (aq)

Key concepts

Precipitation Reactions

In chemistry, a precipitation reaction occurs when two soluble substances in aqueous solutions are combined and form an insoluble product known as a precipitate. A classic example of such a reaction is between sodium sulfide (\( \text{Na}_2\text{S (aq)} \)) and copper(II) sulfate (\( \text{CuSO}_4 \text{(aq)} \)). When these two react, copper(II) sulfide (\( \text{CuS (s)} \)) forms as a solid precipitate that separates from the mixture.
Precipitation reactions are essential to various scientific fields, including chemistry and environmental science, as they help remove unwanted compounds from solutions or identify particular ions. When ions in solution form a precipitate, the product's low solubility in water means it falls out of the solution, thus becoming visible.
Key indicators of a precipitation reaction include:

• The formation of a solid (precipitate) from a liquid solution.
• A visible change, often appearing as cloudiness or sludge.

Ionic Equations

Ionic equations are used to describe the behavior of ions in chemical reactions, particularly those taking place in aqueous solutions. When sodium sulfide and copper(II) sulfate react to form copper(II) sulfide, we can express this reaction using two types of ionic equations: the full ionic equation and the net ionic equation.
In the full ionic equation, all of the ions present in the reaction are shown:\[ \text{2 Na}^+ (\text{aq}) + \text{S}^{2-} (\text{aq}) + \text{Cu}^{2+} (\text{aq}) + \text{SO}_4^{2-} (\text{aq}) \rightarrow \text{CuS(s)} + \text{2 Na}^+ (\text{aq}) + \text{SO}_4^{2-} (\text{aq}) \]
To focus on the formation of the precipitate, the net ionic equation shows only the ions directly involved in creating the precipitate:\[ \text{Cu}^{2+} (\text{aq}) + \text{S}^{2-} (\text{aq}) \rightarrow \text{CuS(s)} \]
The sodium and sulfate ions remain unchanged during the reaction and are considered spectator ions, not participating in the formation of copper(II) sulfide.

Balancing Chemical Equations

Balancing chemical equations is fundamental in chemistry to ensure that mass is conserved in a reaction. It involves making sure the number of atoms for each element is the same on both sides of the equation. For the reaction between sodium sulfide and copper(II) sulfate, the balanced equation is:\[ \text{Na}_2\text{S (aq)} + \text{CuSO}_4 \text{(aq)} \rightarrow \text{CuS (s)} + \text{Na}_2\text{SO}_4 \text{(aq)} \]
To balance the equation, we check each atom:

• Sodium (Na): 2 on both sides
• Sulfur (S): 1 on both sides
• Copper (Cu): 1 on both sides
• Oxygen (O): 4 on both sides

Balancing equations is crucial because it ensures the reaction adheres to the Law of Conservation of Mass, which states that matter cannot be created or destroyed in a closed system. This concept helps chemists understand the stoichiometry of reactions, which is necessary for computing amounts of reactants and products.

Double Replacement Reactions

Double replacement reactions, also known as double displacement or exchange reactions, involve the exchange of ions between two compounds to form two new compounds. Such reactions are characterized by the switch of the cations and anions. In the reaction between sodium sulfide and copper(II) sulfate, the ions swap places:

• The sodium ion \((\text{Na}^+)\) from sodium sulfide pairs with the sulfate ion \((\text{SO}_4^{2-})\) from copper(II) sulfate, forming sodium sulfate.
• The copper ion \((\text{Cu}^{2+})\) from copper(II) sulfate pairs with the sulfide ion \((\text{S}^{2-})\) from sodium sulfide, forming the precipitate copper(II) sulfide.

The reaction is represented as:\[ \text{Na}_2\text{S (aq)} + \text{CuSO}_4 \text{(aq)} \rightarrow \text{CuS (s)} + \text{Na}_2\text{SO}_4 \text{(aq)} \]
This type of chemical reaction is very common in inorganic chemistry and is often used to predict the outcome when mixing aqueous solutions. Understanding double replacement reactions helps learners predict products based on the reactants' ion pairings, making it easier to anticipate and understand outcomes in chemical processes.