Question

When potassium ferrocyanide crystals are heated with conc. \(\mathrm{H}_{2} \mathrm{SO}_{4}\), the gas evolved is (a) \(\mathrm{SO}_{2}\) (b) \(\mathrm{NH}_{3}\) (c) \(\mathrm{CO}_{2}\) (d) \(\mathrm{CO}\)

Short answer

The gas evolved is \\(\mathrm{CO}\\).

Step-by-step solution

Identify the reaction

When potassium ferrocyanide \((K_4[Fe(CN)_6]\) is heated with concentrated sulfuric acid \((H_2SO_4)\), it decomposes. The reaction produces carbon monoxide (CO) among other products. This occurs because concentrated sulfuric acid is a strong dehydrating agent, facilitating the release of gases from the crystal structure.

Write the balanced equation

The balanced chemical equation for the reaction is: \[ K_4[Fe(CN)_6] + 6H_2SO_4 \rightarrow 6CO + 2K_2SO_4 + FeSO_4 + 3(NH_4)_2SO_4 \] This equation shows that carbon monoxide (CO) is evolved as one of the gaseous products of the reaction.

Identify the evolved gas

From the balanced chemical equation, it is evident that carbon monoxide (CO) is evolved during the reaction. Thus, the correct option related to the gas evolved is option (d) \(\mathrm{CO}\).

Key concepts

Exploring Potassium Ferrocyanide

Potassium ferrocyanide is a fascinating inorganic compound with the chemical formula \(K_4[Fe(CN)_6]\). It's often seen as crystalline salt and has historically been used in various applications, like in the dye industry and as a laboratory reagent. A distinct characteristic of potassium ferrocyanide is its relatively stable coordination complex, containing a central iron atom bonded to six cyanide groups.

• Its stability makes it unreactive under normal conditions, yet certain conditions, like heating with strong acids, will lead to its decomposition.
• While the compound is remarkably stable, care should be taken when it's involved in reactions that produce poisonous gases.

When potassium ferrocyanide is heated, especially with strong acids, the crystal structure starts to break down, facilitating the release of various gases, such as carbon monoxide.

The Role of Sulfuric Acid

Concentrated sulfuric acid \((H_2SO_4)\) plays a critical role in many chemical reactions due to its strong acidic and dehydrating properties. When used in reactions, it can influence certain compounds to decompose and evolve gases.

• In the reaction with potassium ferrocyanide, sulfuric acid serves as a strong dehydrating agent, helping to break the chemical bonds and release gases from the complex.
• This property of concentrated sulfuric acid makes it a valuable tool in organic and inorganic synthesis for facilitating specific reactions.

The apparent dehydration capability of \(H_2SO_4\) leads to the evolution of gaseous products, which is pivotal in identifying the nature of the reaction and the types of gases produced.

Understanding Decomposition Reactions

Decomposition reactions are vital in chemistry, involving the breakdown of a compound into simpler substances. In the case of potassium ferrocyanide with sulfuric acid, the role of decomposition is central.

• During the reaction, potassium ferrocyanide decomposes into several products, one being carbon monoxide.
• This type of reaction often requires an external trigger, such as heat or a chemical reactant (e.g., sulfuric acid), to proceed.

Decomposition reactions like these are important for understanding how compounds can be manipulated to yield specific results, including the breakdown of stable structures like the coordination complex in potassium ferrocyanide.

Carbon Monoxide Evolution

Throughout the decomposition reaction, one of the significant observations is the evolution of carbon monoxide (CO). This gas is among the key products evolved when potassium ferrocyanide undergoes decomposition with sulfuric acid.Understanding the conditions under which \(CO\) is produced is essential for safely conducting experiments and industry applications, due to the poisonous nature of the gas.

• It's important to ensure proper ventilation and use of protective equipment when dealing with reactions that produce \(CO\).
• The observation and collection of \(CO\) gas can serve as an indicator or proof of a chemical reaction taking place.

Always handle reactions involving CO evolution with care, acknowledging its poisonous characteristics and ensuring that all safety measures are adhered to, thus ensuring a safe working environment.