Question

The cyclopentadienyl anion \(\left(\mathrm{C}_{5} \mathrm{H}_{5}^{-}\right)\) is an organic ion that can make ionic compounds with positive ions of radioactive elements, such as \(\mathrm{Np}^{3+}\). Balance the following reaction: \(\mathrm{NpCl}_{3}+\mathrm{Be}\left(\mathrm{C}_{5} \mathrm{H}_{5}\right)_{2} \rightarrow \mathrm{Np}\left(\mathrm{C}_{5} \mathrm{H}_{5}\right)_{3}+\mathrm{BeCl}_{2}\)

Short answer

The balanced equation is: \(2 \mathrm{NpCl}_3 + 3 \mathrm{Be}(\mathrm{C}_5\mathrm{H}_5)_2 \rightarrow 2 \mathrm{Np}(\mathrm{C}_5\mathrm{H}_5)_3 + 3 \mathrm{BeCl}_2\).

Step-by-step solution

Understand the Reaction

The given reaction involves neptunium(III) chloride (NpCl₃) reacting with beryllium bis(cyclopentadienide) (Be(C₅H₅)₂) to produce neptunium tris(cyclopentadienide) (Np(C₅H₅)₃) and beryllium chloride (BeCl₂). The goal is to balance the number of atoms of each element on both sides of the reaction.

List the Atoms Involved

Identify the different atoms involved in the reaction. The elements present are Np, Cl, Be, C, and H. Write down the number of each element on both the reactants' and products' sides for the unbalanced reaction.

Balance the Complex Ions First

Focus on the complex ion, the cyclopentadienyl anion (C₅H₅), which forms part of both compounds on each side. There are 2 C₅H₅ anions in Be(C₅H₅)₂ as a reactant, and 3 C₅H₅ anions in Np(C₅H₅)₃ as a product. To balance these, adjust the coefficients to ensure each side has the same total number of C₅H₅ units.

Balance the Cl and Be Atoms

Once the C₅H₅ units are balanced, proceed to balance the chlorine (Cl) and beryllium (Be) atoms. NpCl₃ contains 3 Cl atoms, and BeCl₂ contains 2 Cl atoms. Adjust their coefficients to match the total number of Cl units consumed and produced. Similarly, ensure the total number of Be atoms is balanced.

Adjust and Verify the Coefficients

After adjusting for each type of atom, verify the coefficients of each compound in the equation to ensure all elements are balanced. Confirm that an equal number of each atom type appears on both sides of the equation.

Write the Balanced Equation

The balanced chemical equation should now reflect equal numbers of each atom on both the reactant and product sides: \( 2 \mathrm{NpCl}_{3} + 3 \mathrm{Be} \left( \mathrm{C}_{5} \mathrm{H}_{5} \right)_{2} \rightarrow 2 \mathrm{Np} \left( \mathrm{C}_{5} \mathrm{H}_{5} \right)_{3} + 3 \mathrm{BeCl}_{2} \).

Key concepts

Cyclopentadienyl Anion

The cyclopentadienyl anion, also known as \( \mathrm{C}_5 \mathrm{H}_5^- \), is an organic ion that is commonly found in organometallic chemistry. It consists of a five-carbon ring with alternating double bonds, making it a resonance-stabilized ion. The negative charge is delocalized over the entire carbon ring, contributing to its stability.
This anion is noteworthy because it can form stable complexes with a variety of metals. These complexes are often used in coordination compounds, which have applications in catalysis and as research tools in inorganic chemistry.
In our reaction, the cyclopentadienyl anion (\( \mathrm{C}_5 \mathrm{H}_5^- \)) plays a crucial role in forming the complex with neptunium. This anion is involved in multiple steps of the reaction, requiring that its balance is carefully managed to ensure the reaction proceeds correctly. Learning how to balance such complex ions is essential in achieving the correct stoichiometry in chemical equations.

Neptunium Compounds

Neptunium is a radioactive element, known for its part in the actinide series. It is typically found in oxidation states ranging from +3 to +7, with the +3 state, known as neptunium(III), being common.
In chemical reactions, neptunium can form various compounds, including neptunium chlorides and neptunium cyclopentadienides. In the reaction under study, neptunium(III) participates by reacting with the cyclopentadienyl anion to form neptunium tris(cyclopentadienide) (\( \mathrm{Np} (\mathrm{C}_5 \mathrm{H}_5)_3 \)).
Understanding neptunium's chemistry is vital for nuclear chemistry, as it informs the creation of nuclear fuels and the handling of nuclear waste. Balancing equations involving neptunium compounds often requires attention to both the metal and its complex ions, ensuring the stoichiometry respects both the element and any associated ions.

Chemical Reaction Steps

Balancing chemical equations is a fundamental skill in chemistry, ensuring that mass and charge are conserved in a reaction. The steps involved in balancing the reaction with cyclopentadienyl anion and neptunium compounds involve strategic adjustments to coefficients, starting with the most complex ions.

• **Identify the complex ions**: Start by identifying any complex ions such as the cyclopentadienyl anion. These often appear in multiple species on both sides of the equation and should be balanced first.
• **Balance the compound elements**: Once complex ions are balanced, move to balance the simple ions and atoms, like chlorine and beryllium in this case, by adjusting coefficients.
• **Verify the balance**: Check each atom species to ensure the numbers are matched on both sides. This includes the complex and simple ions, as well as standalone atoms like Be, Np, and Cl.

These steps help in constructing a balanced chemical equation where each atom and charge is correctly represented on both sides. Practicing this approach with different reactants and products enhances one's ability to tackle a variety of chemical reactions accurately.