Question

Write an overall balanced equation for the precipitation reaction that occurs when aqueous copper(II) nitrate is mixed with an aqueous solution of sodium carbonate. Name each reactant and product. Indicate the state of each substance \((\mathrm{s}, \ell, \mathrm{g},\) or aq \()\).

Short answer

The balanced equation is: Cu(NO₃)₂(aq) + Na₂CO₃(aq) → CuCO₃(s) + 2NaNO₃(aq).

Step-by-step solution

Identify the Reactants

The reactants in this reaction are aqueous solutions of copper(II) nitrate and sodium carbonate. We write them as: \(\text{Cu(NO}_3\text{)}_2(aq)\) for copper(II) nitrate and \(\text{Na}_2\text{CO}_3(aq)\) for sodium carbonate.

Predict Product Formation

When copper(II) nitrate and sodium carbonate react, a double displacement reaction occurs, resulting in the formation of copper(II) carbonate and sodium nitrate. Write the products as: \(\text{CuCO}_3(s)\) and \(\text{NaNO}_3(aq)\). Copper(II) carbonate is insoluble in water and precipitates out as a solid, while sodium nitrate remains dissolved.

Write the Initial Equation

Write the initial chemical equation for the reaction before balancing: \[ \text{Cu(NO}_3\text{)}_2(aq) + \text{Na}_2\text{CO}_3(aq) \rightarrow \text{CuCO}_3(s) + \text{NaNO}_3(aq) \]

Balance the Chemical Equation

Balance the equation by ensuring the same number of each type of atom appears on both sides. The balanced equation is: \[ \text{Cu(NO}_3\text{)}_2(aq) + \text{Na}_2\text{CO}_3(aq) \rightarrow \text{CuCO}_3(s) + 2\,\text{NaNO}_3(aq) \]

Indicate States and Name Compounds

In the balanced equation, indicate the state of each compound: Copper(II) nitrate is \((aq)\), sodium carbonate is \((aq)\), copper(II) carbonate is \((s)\), and sodium nitrate is \((aq)\). The final equation with names and states of each compound is: \[ \text{Copper(II) nitrate(aq)} + \text{Sodium carbonate(aq)} \rightarrow \text{Copper(II) carbonate(s)} + \text{Sodium nitrate(aq)} \]

Key concepts

Copper(II) Nitrate

Copper(II) nitrate, with the chemical formula \(\text{Cu(NO}_3\text{)}_2\), is a common inorganic compound used extensively in chemistry. It is an ionic compound composed of one copper ion and two nitrate ions. Copper typically has a +2 oxidation state here. In its anhydrous form, it is a light blue crystalline solid that dissolves well in water.

In aqueous solutions, copper(II) nitrate ions dissociate into copper ions, \(\text{Cu}^{2+}\), and nitrate ions, \(\text{NO}_3^-\). This property makes copper(II) nitrate a suitable candidate in various chemical reactions, particularly in experiments involving precipitation reactions.

Understanding its chemical behavior helps when predicting how it will react with other substances, like sodium carbonate, when forming new products.

Sodium Carbonate

Sodium carbonate, often known as washing soda, is represented by the chemical formula \(\text{Na}_2\text{CO}_3\). It's a white, water-soluble salt that consists of two sodium ions \(\text{Na}^+\) and one carbonate ion \(\text{CO}_3^{2-}\).

Sodium carbonate serves multiple purposes in household and industrial settings, like in cleaning agents and glass production.
When dissolved in water, it effectively separates into its respective ions, making it an excellent candidate for reactions, particularly in aqueous solutions.

In a precipitation reaction with copper(II) nitrate, sodium carbonate provides the carbonate ions necessary for the formation of an insoluble compound, such as copper(II) carbonate. This results in perceptible changes, like the formation of a solid precipitate.

Chemical Equation Balancing

Balancing chemical equations is a cornerstone exercise in chemistry. It ensures that the law of conservation of mass is observed. This means the same number of each type of atom must be present on both the reactant and product sides of the equation.

In our set reaction between copper(II) nitrate and sodium carbonate, after identifying the reactants and predicted products, the unbalanced equation is written out: \[\text{Cu(NO}_3\text{)}_2(aq) + \text{Na}_2\text{CO}_3(aq) \rightarrow \text{CuCO}_3(s) + \text{NaNO}_3(aq)\]

The next step is to balance the equation, ensuring that each side has equal types and numbers of atoms. In this case, adjusting the coefficients gives:\[\text{Cu(NO}_3\text{)}_2(aq) + \text{Na}_2\text{CO}_3(aq) \rightarrow \text{CuCO}_3(s) + 2\,\text{NaNO}_3(aq)\]
By practicing the balancing of equations, students become proficient in chemical reactions and develop a foundational understanding of chemical composition.

Double Displacement Reaction

A double displacement reaction, or metathesis reaction, is a common type of chemical reaction where two compounds exchange parts to produce two new compounds. This reaction is characterized by the swapping of ions between reactants in an aqueous solution.

In the case of copper(II) nitrate reacting with sodium carbonate, both compounds are aqueous, allowing their ions to move freely. As they react, \(\text{Cu}^{2+}\) ions from copper(II) nitrate pair with \(\text{CO}_3^{2-}\) ions from sodium carbonate, leading to the formation of copper(II) carbonate, \(\text{CuCO}_3(s)\), as a precipitate. The \(\text{Na}^+\) ions then combine with \(\text{NO}_3^-\) ions to form soluble sodium nitrate, \(\text{NaNO}_3(aq)\).

These reactions are helpful not only for forming new compounds but also for understanding the behavior of ions in solution, notably for beginners learning about solubility and reaction mechanisms in chemistry.