Question

Identify the element that forms amphoteric oxide.

• A. Al
• B. P
• C. S
• D. Ca

Hint:

Chemistry Tip: Common amphoteric oxides to remember: $Al_2O_3$, $ZnO$, $PbO$, $SnO$, and $BeO$.

Answer 1

The Correct Option is A

Concept: Chemistry (Periodic Table) - Nature of Oxides.

Step 1: Classify the oxide of Calcium (Ca). Calcium is an alkaline earth metal. Metals typically form basic oxides. Calcium oxide ($CaO$) reacts with water to form calcium hydroxide, a base. Thus, it is a basic oxide.

Step 2: Classify the oxides of Phosphorus (P) and Sulfur (S). Phosphorus and Sulfur are non-metals. Non-metals generally form acidic oxides. Oxides like $P_4O_{10}$ and $SO_3$ react with water to form phosphoric acid and sulfuric acid, respectively. Thus, these are acidic oxides.

Step 3: Define amphoteric oxides. Amphoteric oxides are chemical species that exhibit both acidic and basic characteristics. They can react with both strong acids and strong bases to form salts and water.

Step 4: Analyze the oxide of Aluminum (Al). Aluminum forms aluminum oxide ($Al_2O_3$). It reacts with $HCl$ (acid) to form aluminum chloride and with $NaOH$ (base) to form sodium aluminate. Reaction with Acid: $Al_2O_3 + 6HCl \rightarrow 2AlCl_3 + 3H_2O$ Reaction with Base: $Al_2O_3 + 2NaOH + 3H_2O \rightarrow 2Na[Al(OH)_4]$

Step 5: Conclude the correct element. Based on its dual reactivity, aluminum oxide is clearly amphoteric. Therefore, Aluminum is the element from the given options that forms an amphoteric oxide. $$ \therefore \text{The element that forms an amphoteric oxide is Aluminum (Al).} $$