Question

Predict whether each of the following oxides is acidic, basic, , (d) \(\mathrm{CaO}\) amphoteric, or neutral: (a) \(\mathrm{NO}_{2},\) (b) \(\mathrm{CO}_{2},\) (c) \(\mathrm{Al}_{2} \mathrm{O}_{3}\),

Short answer

The types of oxides for the given compounds are: (a) \(\mathrm{NO}_{2}\) - Acidic, (b) \(\mathrm{CO}_{2}\) - Acidic, (c) \(\mathrm{Al}_{2} \mathrm{O}_{3}\) - Amphoteric, and (d) \(\mathrm{CaO}\) - Basic.

Step-by-step solution

Understanding the types of oxides

There are four types of oxides: acidic, basic, amphoteric and neutral. Acidic and basic oxides exhibit their respective acid and base behavior when they react with water. Amphoteric oxides can show both acidic and basic behavior. Neutral oxides do not exhibit any acidic or basic character when they react with water. Generally, non-metal oxides are acidic in nature, while metal oxides are basic. However, some metal oxides like Aluminum oxide are amphoteric, and some non-metal oxides are neutral.

Predicting the type of oxide for \(\mathrm{NO}_{2}\)

Nitrogen dioxide (\(\mathrm{NO}_{2}\)) is a non-metal oxide. Based on the general rule, non-metal oxides are acidic in nature. Thus, we predict that \(\mathrm{NO}_{2}\) is an acidic oxide.

Predicting the type of oxide for \(\mathrm{CO}_{2}\)

Carbon dioxide (\(\mathrm{CO}_{2}\)) is another non-metal oxide. Following the general rule, we predict that \(\mathrm{CO}_{2}\) is an acidic oxide.

Predicting the type of oxide for \(\mathrm{Al}_{2} \mathrm{O}_{3}\)

Aluminum oxide (\(\mathrm{Al}_{2} \mathrm{O}_{3}\)) is a metal oxide. However, aluminum is not just any metal; it is considered amphoteric. This means that its oxide can exhibit both acidic and basic properties. Therefore, we predict that \(\mathrm{Al}_{2} \mathrm{O}_{3}\) is an amphoteric oxide.

Predicting the type of oxide for \(\mathrm{CaO}\)

Calcium oxide (\(\mathrm{CaO}\)) is a metal oxide. According to the general rule, we predict that \(\mathrm{CaO}\) is a basic oxide. In conclusion, the types of oxides for the given compounds are: (a) \(\mathrm{NO}_{2}\) - Acidic (b) \(\mathrm{CO}_{2}\) - Acidic (c) \(\mathrm{Al}_{2} \mathrm{O}_{3}\) - Amphoteric (d) \(\mathrm{CaO}\) - Basic

Key concepts

Acidic Oxides

Acidic oxides are typically formed by non-metals and, in many cases, they react with water to form acids. A common trait of these oxides is that they exhibit acidic behavior by donating protons or accepting electron pairs. Let’s look at some examples:

• Nitrogen dioxide (\(\mathrm{NO}_{2}\)) reacts with water to form nitric acid (\(\mathrm{HNO}_{3}\)).
• Carbon dioxide (\(\mathrm{CO}_{2}\)) reacts with water to form carbonic acid (\(\mathrm{H}_{2}\mathrm{CO}_{3}\)).

These reactions showcase the typical behavior of acidic oxides as they indicate that non-metal oxides, when dissolved in water, tend to lower pH. Therefore, understanding the typical nature of non-metal oxides can help identify potential acidic oxide behavior in chemical reactions.

Basic Oxides

Basic oxides are generally formed by metals and display the characteristics associated with bases. They typically react with acids to form salts and water, which is a key identifying reaction for a base. For instance:

• Calcium oxide (\(\mathrm{CaO}\)) reacts with water to produce calcium hydroxide (\(\mathrm{Ca(OH)}_{2}\)), which is a strong base.

Metal oxides, especially from Group 1 and 2 of the periodic table, tend to be basic. When dissolved in water, they increase the pH of the solution, indicating their basic nature. Recognizing these properties is crucial in predicting their behavior in different chemical environments.

Amphoteric Oxides

Amphoteric oxides are unique because they possess the ability to react like both acids and bases. These oxides do not fit neatly into the typical categorization of acidic or basic, making them versatile in chemical reactions.

• Aluminum oxide (\(\mathrm{Al}_{2}\mathrm{O}_{3}\)) is a classic example. It reacts with both acids, like hydrochloric acid (\(\mathrm{HCl}\)), and bases, like sodium hydroxide (\(\mathrm{NaOH}\)), to form different products.

The dual reactivity is due to the amphoteric nature of such compounds, and they are often found in elements positioned near the metalloid line in the periodic table. Understanding these properties is essential for anticipating their behavior in diverse chemical settings.

Neutral Oxides

Neutral oxides are characterized by their lack of acidic or basic properties. Unlike the other types of oxides, neutral oxides do not react significantly with acids or bases, and they maintain a neutral pH.

• An example of a neutral oxide is nitrous oxide (\(\mathrm{N}_{2}\mathrm{O}\)), which does not readily react to increase or decrease the acidity or basicity of a solution.

These oxides are less common and are often non-metals that do not readily form traditional acids or bases. Understanding and identifying neutral oxides can be useful in applications where non-reactive properties are desired.