Question

Al > Al2O3 > Al(OH)3 > AlPO4 ​

Answer 1

1) 4Al+3O2 = 2Al2O3

2) Al2O3+3H2O= 2Al(OH)3

3) Al(OH)3+H3PO4= AlPO4+ 3H2O

Answer 2

The given sequence represents a decreasing order of the solubility of compounds containing aluminum (Al) in water. Here's a breakdown of each compound:

1. Al (aluminum): Aluminum is a metal and is not soluble in water. It does not dissociate into ions when placed in water. Therefore, it has the lowest solubility among the compounds listed.

2. Al2O3 (aluminum oxide): Aluminum oxide is also known as alumina. It is sparingly soluble in water and has low solubility. In water, it can react with hydroxide ions to form aluminum hydroxide.

3. Al(OH)3 (aluminum hydroxide): Aluminum hydroxide is more soluble in water than aluminum oxide. It can dissociate into aluminum ions (Al3+) and hydroxide ions (OH-) when placed in water. It is often used as an antacid due to its ability to neutralize excess stomach acid.

4. AlPO4 (aluminum phosphate): Aluminum phosphate is the most soluble compound among the ones listed. It can dissociate into aluminum ions (Al3+) and phosphate ions (PO43-) when dissolved in water. It is commonly used in various industrial applications, including as a catalyst and in the production of ceramics.

In summary, the solubility of aluminum compounds in water decreases in the order: AlPO4 > Al(OH)3 > Al2O3 > Al.