Question

\(\mathrm{A}+\mathrm{C}+\mathrm{Cl}_{2} \frac{\text { High temperature }}{\text { Of about } 1000 \mathrm{~K}} \mathrm{~B}+\mathrm{CO}\) \(\mathrm{B}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{C}+2 \mathrm{HCl}\) Compound \(\mathrm{B}\) is found in polymeric chain structure and is an electron deficient molecule. B must be: (a) \(\mathrm{BeCl}_{2}\) (b) \(\mathrm{BeO} \cdot \mathrm{Be}(\mathrm{OH})_{2}\) (c) \(\mathrm{Be}(\mathrm{OH})_{2}\) (d) \(\mathrm{BeO}\)

Short answer

B is \( \mathrm{BeCl}_{2} \).

Step-by-step solution

Analyze the First Reaction

The reaction given is \( \mathrm{A}+\mathrm{C}+\mathrm{Cl}_{2} \xrightarrow{1000 \mathrm{~K}} \mathrm{~B}+\mathrm{CO}\). High temperature leads to the formation of \( \mathrm{B} \) and \( \mathrm{CO} \), suggesting \( \mathrm{A} \) might be a compound breaking down to release carbon monoxide, a sign of an oxide or carbonate.

Analyze Properties of Compound B

The statement describes \( \mathrm{B} \) as found in a polymeric chain structure and an electron-deficient molecule. Only a small number of compounds involving beryllium (which has similar properties to B) are like this. Of the options provided, \( \mathrm{BeCl}_{2} \) fits both of these characteristics.

Check Second Reaction Consistency

The second reaction \( \mathrm{B}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{C}+2 \mathrm{HCl} \) describes \( \mathrm{B} \) reacting with water to release \( \mathrm{HCl} \). \( \mathrm{BeCl}_{2} \), an electron-deficient halide, fits well since reacting with water would produce \( \mathrm{HCl} \), consistent with the equation.

Confirm Choice Using Electron Deficiency and Structure

\( \mathrm{BeCl}_{2} \) is known for forming polymeric structures and is electron-deficient due to its two 7-electron beryllium atom bonds, aligning with the problem statement's description of \( \mathrm{B} \).

Key concepts

Polymeric Chain Structure

In chemistry, polymeric chain structures are quite common in certain compounds where multiple units are linked to form long, repeating sequences. Polymeric chains can exhibit unique properties such as strength, flexibility, and the ability to form coils and networks.

For beryllium chloride,

• The structure involves beryllium centers linked through chlorines bridging between them.
• It is mostly found in the solid-state as a polymer where each beryllium atom is kinda sandwiched between two chlorine atoms in a chain-like manner, forming a linear chain.

These structures are held together through interactions that are not just simple ionic or covalent, but involve other more complex bonding forms.

Understanding these structures is crucial for understanding how certain chemicals behave, especially in industrial or high-temperature situations.

Electron Deficient Molecule

An electron deficient molecule is often a molecule where the central atom does not have a full octet, often leading to interesting properties like the ability to form unique bonds. This is significantly different from conventional molecules which satisfy the octet rule.

Beryllium compounds, like

• \[\text{BeCl}_2\]

are notable examples of being electron deficient because the beryllium atom only has four electrons available to share typically.

Due to this, these molecules often draw electrons from other atoms or form multi-center bonds, like the polymeric structures we discussed. This deficiency is what enables beryllium chloride to form its unique polymeric chain.

While this phenomenon might seem rare, it’s crucial for fields involving materials science and advanced chemistry.

Beryllium Compounds

Beryllium compounds have unique properties because of how beryllium behaves chemically. This element in the periodic table sits with alkaline earth metals but often behaves differently due to its small size and relatively high ionization energy. Beryllium forms compounds like

• \[\text{BeCl}_2\]

but unlike other group 2 elements, it forms covalent rather than ionic bonds.

Its compounds can be quite fascinating:

• They often resist typical metallic properties.
• They form structures featuring electron-deficient bonding, as already mentioned.

Understanding beryllium compounds is essential especially in fields like aerospace engineering and nuclear applications because their materials possess an optimal ratio of strength to weight.

In everyday chemistry and more advanced applications, these compounds help us explore beyond traditional bonding and properties.