Question

Write balanced equations for the following reactions: (a) the thermal decomposition of \(\left[\mathrm{NH}_{4}\right]_{2}\left[\mathrm{BeF}_{4}\right]\) (b) the reaction between \(\mathrm{NaCl}\) and \(\mathrm{BeCl}_{2}\) (c) the dissolution of BeF \(_{2}\) in water.

Short answer

Balanced equations: (a) \([\mathrm{NH}_{4}]_{2}[\mathrm{BeF}_{4}] \rightarrow 2\mathrm{NH_{3}} + 4\mathrm{HF} + \mathrm{BeF_{2}}\) (b) \(\mathrm{NaCl} + \mathrm{BeCl}_{2} \rightarrow \mathrm{NaBeCl}_{3}\) (c) \(\mathrm{BeF_{2}} \rightarrow \mathrm{Be^{2+}} + 2\mathrm{F^{-}}\)

Step-by-step solution

Understand the Reaction Type

For part (a), identify thermal decomposition which involves heating a compound to break it down into simpler substances. In part (b), a typical reaction involves the exchange of ions between compounds. Part (c) involves dissolution, where a solid dissolves in a liquid to form ions in solution.

Write the Reactants

For part (a), start with the reactant \([\mathrm{NH}_{4}]_{2}[\mathrm{BeF}_{4}]\). For part (b), the reactants are \(\mathrm{NaCl}\) and \(\mathrm{BeCl}_{2}\). In part (c), write down the reactant \(\mathrm{BeF}_{2}\).

Determine the Products

In part (a), thermal decomposition of \([\mathrm{NH}_{4}]_{2}[\mathrm{BeF}_{4}]\) yields \(\mathrm{NH}_{3}\), \(\mathrm{HF}\), and \(\mathrm{BeF}_{2}\). In part (b), the reaction produces \(\mathrm{NaBeCl}_{3}\). In part (c), \(\mathrm{BeF}_{2}\) dissolves in water separating into ions \(\mathrm{Be}^{2+} + 2\mathrm{F}^{-}\).

Balance the Equations

For part (a), balance the decomposition reaction: \(\mathrm{[NH_{4}]_{2}[BeF_{4}]} \rightarrow 2\mathrm{NH_{3}} + 4\mathrm{HF} + \mathrm{BeF_{2}}\). For part (b), balance with: \(\mathrm{NaCl} + \mathrm{BeCl_{2}} \rightarrow \mathrm{NaBeCl_{3}}\).For part (c), ensure the dissociation is balanced: \(\mathrm{BeF_{2}} \rightarrow \mathrm{Be^{2+}} + 2\mathrm{F^{-}}\).

Key concepts

Thermal Decomposition

Thermal decomposition involves heating a compound, causing it to break down into simpler substances. This type of reaction is crucial in chemistry as it helps to understand how compounds destabilize and decompose under heat. For example, in the thermal decomposition of \( [\mathrm{NH}_{4}]_{2}[\mathrm{BeF}_{4}] \), the compound breaks down when heated, resulting in the formation of \( \mathrm{NH}_{3} \), \( \mathrm{HF} \), and \( \mathrm{BeF}_{2} \).

• \( [\mathrm{NH}_{4}]_{2}[\mathrm{BeF}_{4}] \) is the original compound.
• When heated, it decomposes into \( 2\mathrm{NH}_{3} \) (ammonia), \( 4\mathrm{HF} \) (hydrogen fluoride), and \( \mathrm{BeF}_{2} \) (beryllium fluoride).

The balanced equation for this reaction is: \[ [\mathrm{NH}_{4}]_{2}[\mathrm{BeF}_{4}] \rightarrow 2\mathrm{NH}_{3} + 4\mathrm{HF} + \mathrm{BeF}_{2} \]This equation shows the importance of conserving mass, meaning the number of each type of atom on both sides of the equation should remain equal. Understanding these reactions is useful for predicting how similar compounds might behave under thermal conditions.

Ion Exchange Reactions

Ion exchange reactions involve the swapping of ions between compounds, which is a common occurrence in chemical processes. An example of such a reaction is between \( \mathrm{NaCl} \) (sodium chloride) and \( \mathrm{BeCl}_{2} \) (beryllium chloride).
This specific reaction results in the formation of a new compound, \( \mathrm{NaBeCl}_{3} \).

• The equation for this ion exchange reaction is:
• \( \mathrm{NaCl} + \mathrm{BeCl}_{2} \rightarrow \mathrm{NaBeCl}_{3} \)

This equation must be balanced to satisfy the conservation of mass. In this exchange:

• The chloride ions (\( \mathrm{Cl}^{-} \)) are shared between sodium \( \mathrm{Na}^{+} \) and beryllium \( \mathrm{Be}^{2+} \) ions.
• Ion exchange reactions are valuable in purification processes, such as water treatment, where unwanted ions are exchanged with more desirable ions.

Dissolution in Water

Dissolution is the process where a substance dissolves in a liquid, typically forming a solution. When \( \mathrm{BeF}_{2} \) (beryllium fluoride) dissolves in water, it dissociates completely, separating into beryllium ions and fluoride ions. This is an important aspect of chemical reactions as it helps in understanding solubility and the formation of ionic solutions.

• The dissolution reaction can be represented as:
• \( \mathrm{BeF}_{2} \rightarrow \mathrm{Be^{2+}} + 2\mathrm{F^{-}} \)

In this reaction:

• \( \mathrm{BeF}_{2} \) is the solute, which breaks down into ions when dissolved.
• Water acts as a solvent, facilitating the separation of the atoms.

Dissolution in water is pivotal in various applications, such as in analytical chemistry for preparing solutions that can then be used in titration and spectrometry. This property is utilized in many industrial and scientific processes to achieve precise chemical reactions.