Question

Starting with aluminum, describe with balanced equations how you would prepare (a) \(\mathrm{Al}_{2} \mathrm{Cl}_{6}\) (b) \(\mathrm{Al}_{2} \mathrm{O}_{3}\) (c) \(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3},\) (d) \(\mathrm{NH}_{4} \mathrm{Al}\left(\mathrm{SO}_{4}\right)_{2} \cdot 12 \mathrm{H}_{2} \mathrm{O}\).

Short answer

Combine aluminum with chlorine, convert to Al2O3 with hydrochloric acid, and react with sulfuric acid for Al2(SO4)3, then add (NH4)2SO4 for NH4Al(SO4)2·12H2O.

Step-by-step solution

Preparing Al2Cl6

Begin with metallic aluminum and react it with chlorine gas. The balanced chemical reaction is: \[ 2 ext{Al(s)} + 3 ext{Cl}_2(g) ightarrow ext{Al}_2 ext{Cl}_6(s) \] Here, aluminum reacts with chlorine gas to produce aluminum chloride.

Converting Al2Cl6 to Al2O3

Next, convert aluminum chloride to aluminum oxide. To do this, react \( ext{Al}_2 ext{Cl}_6 \) with water and hydroxide. The balanced drying reaction is:\[ ext{Al}_2 ext{Cl}_6(s) + 6 ext{H}_2 ext{O(l)} ightarrow 2 ext{Al(OH)}_3(s) + 6 ext{HCl(aq)} \]Follow this with heating (calcination):\[ 2 ext{Al(OH)}_3(s) ightarrow ext{Al}_2 ext{O}_3(s) + 3 ext{H}_2 ext{O(g)} \]This results in the conversion of aluminum hydroxide to aluminum oxide.

Preparing Al2(SO4)3

To convert aluminum oxide to aluminum sulfate, react it with sulfuric acid. The balanced chemical equation is:\[ ext{Al}_2 ext{O}_3(s) + 3 ext{H}_2 ext{SO}_4(aq) ightarrow ext{Al}_2( ext{SO}_4)_3(aq) + 3 ext{H}_2 ext{O(l)} \]Here, sulfuric acid reacts with aluminum oxide to produce aluminum sulfate.

Preparing NH4Al(SO4)2 · 12H2O

Finally, prepare ammonium aluminum sulfate dodecahydrate by reacting aluminum sulfate with ammonium sulfate in the presence of water. The balanced reaction is:\[ ext{Al}_2( ext{SO}_4)_3(aq) + ext{(NH}_4)_2 ext{SO}_4(aq) + 24 ext{H}_2 ext{O(l)} ightarrow 2 ext{NH}_4 ext{Al(SO}_4)_2 ext{· 12H}_2 ext{O(s)} \]This reaction yields ammonium aluminum sulfate hydrated crystals.

Key concepts

Aluminum Chloride Preparation

To prepare aluminum chloride (\(\mathrm{Al}_{2}\mathrm{Cl}_{6}\)), you start with metallic aluminum and add chlorine gas. This chemical reaction is straightforward and crucial for various industrial applications. The balanced equation is: \[\mathrm{2\ Al(s) + 3\ Cl_2(g) \longrightarrow \ Al_2Cl_6(s)}\]- **Aluminum (Al):** A lightweight, silvery metal that is very reactive.- **Chlorine gas (Cl\(_2\)):** A yellow-green gas used in a wide range of chemical syntheses.When aluminum and chlorine combine, they produce aluminum chloride in a solid form. This reaction should be done in a controlled environment to ensure safety, as chlorine gas can be hazardous. Aluminum chloride is widely used in the chemical industry, particularly as a catalyst in various reactions.

Aluminum Oxide Synthesis

The synthesis of aluminum oxide (\(\mathrm{Al}_{2}\mathrm{O}_{3}\)), also called alumina, involves two main steps. First, aluminum chloride (\(\mathrm{Al}_{2}\mathrm{Cl}_{6}\)) is reacted with water to form aluminum hydroxide (\(\mathrm{Al(OH)}_3\)). Then, this hydroxide is heated to produce aluminum oxide. The balanced chemical reactions are:1. Hydration:\[\mathrm{Al_2Cl_6(s) + 6\ H_2O(l) \longrightarrow 2\ Al(OH)_3(s) + 6\ HCl(aq)}\]2. Calcination:\[\mathrm{2\ Al(OH)_3(s) \longrightarrow Al_2O_3(s) + 3\ H_2O(g)}\]- **Water Aid:** Water helps break down aluminum chloride into aluminum hydroxide.- **Heat Treatment:** Applying heat decomposes aluminum hydroxide into alumina and water vapor.Aluminum oxide is a vital compound used in ceramics and various industrial processes due to its hardness and high melting point.

Aluminum Sulfate Formation

The formation of aluminum sulfate (\(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}\)) requires reacting aluminum oxide with sulfuric acid. This reaction is critical in producing aluminum sulfate used in water purification, among other applications. The balanced chemical equation for this process is:\[\mathrm{Al_2O_3(s) + 3\ H_2SO_4(aq) \longrightarrow Al_2(SO_4)_3(aq) + 3\ H_2O(l)}\]- **Sulfuric Acid (H\(_2\)SO\(_4\)):** A strong acid that facilitates the transformation of alumina.- **Water Outcome:** Water is a byproduct of this reaction.Aluminum sulfate produced from this reaction is commonly used in dyeing fabrics and purifying drinking water, making it an essential compound in daily applications.

Ammonium Aluminum Sulfate Hydrate

Ammonium aluminum sulfate hydrate, often known as ammonium alum, is a compound formed by combining aluminum sulfate and ammonium sulfate in water. This process results in the formation of hydrated crystals. The balanced equation is:\[\mathrm{Al_2(SO_4)_3(aq) + (NH_4)_2SO_4(aq) + 24\ H_2O(l) \longrightarrow 2\ NH_4Al(SO_4)_2 \cdot 12H_2O(s)}\]- **Combination Play:** Aluminum and ammonium sulfate react to form a solid in water.- **Water’s Role:** Acts as the medium for reaction and crystallization.Ammonium alum is useful in everything from water purification and paper making to astringents and food additives. The formation of its crystals showcases the beautiful chemistry involved in hydration reactions. This compound is notable for its unique properties like solubility and ability to form large, clear crystals.