Question

The false statement among the following is (1) \(\mathbf{\Lambda n h y d r o u s} \mathbf{~} \mathbf{\Lambda l C l}_{3}\) is covalent. (2) IIydrated \(\mathbf{\Lambda l C l}_{3} \cdot 6 \mathrm{II}_{2} \mathrm{O}\) is ionic. (3) \Lambdanhydrous \(\Lambda 1 \mathrm{Cl}_{3}\) is a Lewis acid. (4) IIydrated \(\mathbf{\Lambda l C l}_{3} \cdot 6 \mathrm{II}_{2} \mathrm{O}\) is Lewis acid.

Short answer

Statement 4 is false. Hydrated \( \textbf{AlCl}_{3} \cdot 6 \text{H}_2 \text{O} \) is not a Lewis acid.

Step-by-step solution

Identify the Covalent and Ionic Compounds

Check if anhydrous \(\textbf{AlCl}_{3}\) and hydrated \( \textbf{AlCl}_{3} \cdot 6 \text{H}_2 \text{O} \) are covalent or ionic. Anhydrous \( \textbf{AlCl}_{3} \) is covalent because it forms a dimer through chlorine bridges. Hydrated \(\textbf{AlCl}_{3} \cdot 6 \text{H}_2 \text{O} \) contains water molecules that coordinate to the \( \text{Al}^{3+} \) ions, making the compound ionic.

Check if Anhydrous \( \textbf{AlCl}_{3} \) is a Lewis Acid

Identify if anhydrous \( \textbf{AlCl}_{3} \) acts as a Lewis acid. \( \textbf{AlCl}_{3} \) is a Lewis acid as it can accept electron pairs due to the presence of an empty orbital on the aluminum atom.

Check if Hydrated \( \textbf{AlCl}_{3} \cdot 6 \text{H}_2 \text{O} \) is a Lewis Acid

Determine if \( \textbf{AlCl}_{3} \cdot 6 \text{H}_2 \text{O} \) can act as a Lewis acid. The hydrate form already has aluminum coordinated with H2O molecules, reducing its ability to act as a Lewis acid effectively compared to the anhydrous form.

Identify the False Statement

Compare the statements given: (1) \( \textbf{AlCl}_{3} \) is covalent (true), (2) \( \textbf{AlCl}_{3} \cdot 6 \text{H}_2 \text{O} \) is ionic (true), (3) \( \textbf{AlCl}_{3} \) is a Lewis acid (true), (4) \( \textbf{AlCl}_{3} \cdot 6 \text{H}_2 \text{O} \) is a Lewis acid (false). Thus, the false statement is: \textbf{ii}ydrated \( \textbf{AlCl}_{3} \cdot 6 \text{H}_2 \text{O} \) is a Lewis acid.

Key concepts

Covalent Compounds

Covalent compounds are created when two or more atoms share electrons, instead of giving them away or taking them. These atoms form molecules where the shared electrons belong to both atoms in the bond. An example of a covalent compound is anhydrous \(\textbf{AlCl}_3\), where aluminum and chlorine atoms share electrons, forming a stable molecule.

• Covalent bonds are typically found in compounds with nonmetals.
• These bonds can be single, double, or triple, depending on the number of shared electron pairs.

Understanding covalent bonds is crucial in predicting the properties of the compound, such as its melting and boiling points. These compounds generally have lower melting and boiling points compared to ionic compounds.

Ionic Compounds

Ionic compounds are formed when atoms transfer electrons from one to another, resulting in oppositely charged ions that are attracted to each other. This type of bond generally occurs between metals and nonmetals. An example is hydrated \( \textbf{AlCl}_3 \cdot 6 \text{H}_2 \text{O} \), where aluminum loses electrons to chlorine, forming \( \text{Al}^{3+} \) and \( \text{Cl}^{-} \) ions, with water molecules stabilizing the structure.

• Ionic bonds create a crystalline lattice, which contributes to high melting and boiling points.
• These compounds are often soluble in water and conduct electricity when dissolved.

Identifying whether a compound is ionic or covalent helps predict how it will behave in different environments, such as in water or when exposed to heat.

Coordination Chemistry

Coordination chemistry deals with coordination compounds, where a central metal atom or ion is bonded to surrounding molecules or ions, called ligands. These ligands donate pairs of electrons to the metal, creating a complex. For instance, in hydrated \( \textbf{AlCl}_3 \cdot 6 \text{H}_2 \text{O} \), water molecules act as ligands, coordinating to the \( \text{Al}^{3+} \) ion.

• The metal-ligand bond is known as a coordinate covalent bond, where both electrons in the bond originate from the ligand.
• Coordination compounds can exhibit various geometries, such as octahedral or tetrahedral, based on the number of ligands.

Understanding the principles of coordination chemistry is important in many fields, including catalysis and material science.

Hydration of Compounds

Hydration refers to the addition of water molecules to a substance, which can significantly alter its properties. This process is especially important in coordination chemistry, as seen with hydrated \( \textbf{AlCl}_3 \cdot 6 \text{H}_2 \text{O} \). In this case, the aluminum ions are surrounded by water molecules, forming a stable hydrated complex.

• Hydration can change the solubility, reactivity, and phase of a compound.
• The number of water molecules associated with a compound is often indicated in its chemical formula.

Recognizing the effects of hydration helps in understanding the compound's behavior in aqueous environments and its overall stability.