Question

Arrange the following oxides in order of increasing acidity: \(\mathrm{K}_{2} \mathrm{O}, \mathrm{BaO}, \mathrm{ZnO}, \mathrm{H}_{2} \mathrm{O}, \mathrm{CO}_{2}, \mathrm{SO}_{2}\)

Short answer

The order of oxides in increasing acidity is: \(\mathrm{BaO}\), \(\mathrm{K}_{2} \mathrm{O}\), \(\mathrm{ZnO}\), \(\mathrm{H}_{2} \mathrm{O}\), \(\mathrm{CO}_{2}\), \(\mathrm{SO}_{2}\).

Step-by-step solution

Identify the type of each oxide

Based on the element that the oxide is formed from, we can determine whether it is a metallic, amphoteric, or acidic oxide. 1. \(\mathrm{K}_{2} \mathrm{O}\): K is potassium which is a metal, so this is a metallic oxide. 2. \(\mathrm{BaO}\): Ba is barium, which is a metal, so this is a metallic oxide. 3. \(\mathrm{ZnO}\): Zn is zinc, which is a borderline metal, so this is an amphoteric oxide. 4. \(\mathrm{H}_{2} \mathrm{O}\): H is a non-metal, so this is an acidic oxide. 5. \(\mathrm{CO}_{2}\): C and O are non-metals, so this is an acidic oxide. 6. \(\mathrm{SO}_{2}\): S and O are non-metals, so this is an acidic oxide.

Arrange the metallic oxides in increasing order of acidity

As the basic character of metallic oxides increases from right to left and down the periodic table, \(\mathrm{BaO}\) is more basic (\(\mathrm{Ba}\) is at the lower left side) than \(\mathrm{K}_{2} \mathrm{O}\) (\(\mathrm{K}\) is in the middle left side). This means \(\mathrm{BaO}\) has a comparatively weaker acidic character than \(\mathrm{K}_{2} \mathrm{O}\).

Arrange the acidic oxides in increasing order of acidity

As the acidic character of acidic oxides increases from left to right and up the periodic table, \(\mathrm{H}_{2} \mathrm{O}\) has the weakest acidic character (H being farthest left and closest to top). The acidic character of \(\mathrm{CO}_{2}\) is lesser than that of \(\mathrm{SO}_{2}\). Therefore, the order of acidic oxides with increasing acidity is \(\mathrm{H}_{2} \mathrm{O}\), \(\mathrm{CO}_{2}\), and \(\mathrm{SO}_{2}\).

Combine the oxide lists

Now that we have arranged the acidic and metallic oxides in order of increasing acidity, we can put amphoteric oxide (\(\mathrm{ZnO}\)) between the metallic and acidic oxides. So the final order of oxides in increasing acidity is: \(\mathrm{BaO}\), \(\mathrm{K}_{2} \mathrm{O}\), \(\mathrm{ZnO}\), \(\mathrm{H}_{2} \mathrm{O}\), \(\mathrm{CO}_{2}\), \(\mathrm{SO}_{2}\)

Key concepts

Metallic Oxide

Metallic oxides are compounds formed by the reaction of metals with oxygen. These oxides usually have a basic character. When metallic oxides dissolve in water, they often form metal hydroxides, which are basic in nature. This basicity is due to the presence of the oxide ion

• Basic Properties: Metallic oxides tend to react with acids to form salt and water. This shows their ability to neutralize acids.
• Examples: In the exercise, potassium oxide (\(\mathrm{K}_{2} \mathrm{O}\)) and barium oxide (\(\mathrm{BaO}\)) are both metallic oxides. Potassium oxide is more acidic than barium oxide because it is located higher up on the periodic table.

Understanding the properties of metallic oxides helps predict their behavior in reactions, particularly with acidic substances.

Amphoteric Oxide

Amphoteric oxides are unique because they exhibit both acidic and basic properties. This dual nature allows them to react with both acids and bases, forming salts in both cases. Essentially, they can donate or accept electrons depending on the environment. The amphoteric nature is often found in oxides of elements located on the border between metals and non-metals on the periodic table.

• Example: Zinc oxide (\(\mathrm{ZnO}\)) is an amphoteric oxide, as mentioned in the exercise. It reacts with acids like hydrochloric acid to give zinc chloride and water, showcasing its basic side. Conversely, it reacts with strong bases, indicating its acidic character.
• Chemical Behavior: This versatility in chemical reactions is due to the ability of amphoteric oxides to either gain or lose protons, adapting to the surroundings.

Amphoteric oxides play a critical role in various chemical processes due to this adaptability.

Acidic Oxide

Acidic oxides are often formed by non-metals reacting with oxygen. They tend to exhibit acidic properties and can react with bases to produce salt and water. These oxides are typically gases at room temperature and are soluble in water to form acids. Their ability to donate protons (H+) in reactions underlines their acidic behavior.

• Chemical Characteristics: When dissolved in water, acidic oxides tend to form acidic solutions. For instance, carbon dioxide (\(\mathrm{CO}_{2}\)) dissolves in water to form carbonic acid.
• Examples: As outlined in the exercise, \(\mathrm{H}_2\mathrm{O}\), \(\mathrm{CO}_{2}\), and \(\mathrm{SO}_{2}\) are classic acidic oxides. \(\mathrm{H}_2\mathrm{O}\) is the least acidic since it is located at the top left of the periodic table.

These oxides are essential in understanding environmental chemistry, especially in phenomena like acid rain where \(\mathrm{SO}_{2}\) plays a crucial role.