Key Difference – Acidic vs Basic Oxides
Oxides are compounds having at least one oxygen atom attached to another element. Oxides are formed when a particular element reacts with oxygen. Since oxygen is highly reactive in nature, it reacts with metallic and non-metallic elements and forms oxides of those elements. This oxygen comes from either air or water. Due to high electronegativity, oxygen can react with almost all the elements except noble gases. The major types of oxides include acidic oxides, basic oxides, amphoteric oxides and neutral oxides. This classification is done according to the nature and properties of those oxides. The key difference between acidic and basic oxides is that acid oxides form acids when dissolved in water whereas basic oxides form bases when dissolved in water.
CONTENTS
1. Overview and Key Difference
2. What are Acidic Oxides
3. What are Basic Oxides
4. Side by Side Comparison – Acidic vs Basic Oxides
5. Summary
What are Acidic Oxides?
Acidic oxides are formed when a non-metal reacts with oxygen. Acidic oxides react with water and produce aqueous acids. These acid compounds are composed of oxygen, hydrogen atoms along with the atoms of that particular non-metal linked via covalent bonds. These acid compounds are called acid anhydrides since they produce the acid compound of that oxide when dissolved in water. For example, sulfur dioxide is called sulfurous anhydride and sulfur trioxide is called sulfuric anhydride. Acid oxides can react with a base to produce its salt. Usually, acid oxides have low melting points and low boiling points except for oxides like silicon dioxide which tend to form giant molecules. These oxides will dissolve in bases and form a salt and water. When an acidic oxide is dissolved in water, it will decrease the pH of the water sample due to the formation of H+ ions. Some common examples of acidic oxides are, CO2, P2O5, NO2, SO3, etc.. Following reaction is an example for dissolving acidic oxide in water.
SO3(s) + H2O(l) → H2SO4(aq)
Figure 01: Nitrogen Dioxide at different temperatures
What are Basic Oxides?
Basic oxides are formed as a result of a reaction of oxygen with metals. Due to the difference in electronegativity between oxygen and metals, most of the basic oxides are ionic in nature. Thus, they have ionic bonds between atoms. These oxides react with water actively, producing basic compounds. These oxides also react with acids and form a salt and water. When a basic oxide is added to water, the pH of water increases due to the formation of hydroxyl ions (OH–). Some examples of common basic oxides are, Na2O, CaO, MgO, etc. The following example shows the dissolving of a basic oxide in water.
Na2O(s) + H2O(l) → NaOH(aq)
Figure 02: Magnesium Oxide (Example of a Basic Oxide)
What is the Difference Between Acidic and Basic Oxides?
Acidic vs Basic Oxides |
|
| Acidic oxides are formed when oxygen reacts with non-metals. | Basic oxides are formed when oxygen reacts with metals. |
| Reaction with Water | |
| Acidic oxides react with water by forming acidic compounds. | Basic oxides react with water forming basic compounds. |
| Reaction with Acid | |
| Acidic oxides do not react with acids. | Basic oxides react with acids by forming a salt. |
| Reaction with Base | |
| Acidic oxides react with bases by forming a salt. | Basic oxides do not react with bases. |
| Bonds | |
| Acidic oxides have covalent bonds. | Basic oxides have ionic bonds. |
| Effects on pH | |
| When acidic oxides are dissolved in water it decreases the pH. | Dissolving of basic oxides causes increasing the pH. |
| Other Names | |
| Acidic oxides are also known as acid anhydrides. | Basic oxides are also called as base anhydrides. |
Summary – Acidic vs Basic Oxides
Oxides are compounds having at least one oxygen atom bonded to another element. This element can be a metal or a non-metal. Oxides can be acidic or basic according to their properties. If a particular oxide can react with an acid but not with a base, it is called a basic oxide. If an oxide reacts with a base but not with acids, it is an acidic oxide. The key difference between acidic oxides and basic oxides is that acid oxides form acids when dissolved in water whereas basic oxides form bases when dissolved in water.
References:
1.Dunk, V., 2013. slide share. [Online]
Available at: https://www.slideshare.net/bsvab/acidic-and-basic-oxides-16541388 [Accessed 26 05 2017].
2. Chang, R., 2010. chemistry. 10th ed. NewYork: McGraw-Hill.
3. Hesthra, B., 2016. libretexts. [Online] Available at: https://chem.libretexts.org/Core/Inorganic_Chemistry/Descriptive_Chemistry/Main_Group_Reactions/Compounds/Oxides [Accessed 26 05 2017].
Image Courtesy:
1. “Nitrogen dioxide at different temperatures” By Eframgoldberg – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Magnesium oxide” By Walkerma. Own work (based on copyright claims) (Public Domain) via Commons Wikimedia