Problem 136 - Chemistry

Question

The three common chromium oxides are \(\mathrm{CrO}, \mathrm{Cr}_{2} \mathrm{O}_{3},\) and \(\mathrm{CrO}_{3}\). If \(\mathrm{Cr}_{2} \mathrm{O}_{3}\) is amphoteric, what can you say about the acid-base properties of \(\mathrm{CrO}\) and \(\mathrm{CrO}_{3} ?\)

Step-by-Step Solution

Answer

\(\mathrm{CrO}\) is basic; \(\mathrm{CrO}_{3}\) is acidic.

Step 1: Understand Amphoteric Substance

An amphoteric substance can act as both an acid and a base. \(\mathrm{Cr}_{2}\mathrm{O}_{3}\) is given as amphoteric, meaning it can react with both acids and bases depending on the conditions.

Step 2: Assess Properties of \(\mathrm{CrO}\)

\(\mathrm{CrO}\) is known as a basic oxide. Basic oxides typically react with acids to form salt and water, indicating that \(\mathrm{CrO}\) more likely behaves as a base.

Step 3: Assess Properties of \(\mathrm{CrO}_{3}\)

\(\mathrm{CrO}_{3}\) is known as an acidic oxide. Acidic oxides typically react with bases to form salt and water, which indicates that \(\mathrm{CrO}_{3}\) behaves as an acid.

Step 4: Conclusion on the Acid-Base Properties

Based on their reactions with acids and bases: \(\mathrm{CrO}\) behaves as a basic oxide, while \(\mathrm{CrO}_{3}\) acts as an acidic oxide.

Key Concepts

Amphoteric Substances

An amphoteric substance is quite versatile because it can behave as both an acid and a base. This dual nature means that at times, it can donate a proton just like an acid, and in other situations, it can accept a proton, similar to a base. A well-known example of an amphoteric substance is chromium(III) oxide, or \( \mathrm{Cr}_{2}\mathrm{O}_{3} \). This substance can participate in reactions with both acids and bases. Here’s how it functions:

• When \( \mathrm{Cr}_{2}\mathrm{O}_{3} \) reacts with acids, it tends to donate electrons or oxide ions, thus showing basic behavior.
• Conversely, when it encounters bases, it reacts by accepting protons or neutralizing the base, thereby exhibiting acidic properties.

Understanding amphoteric substances is crucial because it highlights the balance between acidic and basic characteristics in a single compound. This flexibility is important in various chemical processes and applications.

Acidic and Basic Oxides

Oxides are compounds that include oxygen and one other element, and they can manifest as either acidic or basic. The type of oxide determines how it reacts with other substances. Let’s explore this:

• Basic Oxides: These oxides typically contain metals and exhibit basic properties. They react with acids to form salt and water. \( \mathrm{CrO} \), or chromium(II) oxide, is a classic example of a basic oxide. Its behavior can be observed when it interacts with acids and neutralizes them, producing salt and water.
• Acidic Oxides: These usually involve non-metals and possess acidic characteristics. They react with bases to form salt and water. For instance, \( \mathrm{CrO}_{3} \), or chromium(VI) oxide, is known as an acidic oxide. It reacts readily with bases, leading to neutralization and the formation of salt and water.

These oxides highlight the diverse nature of chemical reactions based on the oxide's characteristics, paving the way for various applications in chemical industries.

Acid-Base Properties

The acid-base properties of compounds are foundational in chemistry, defining how they react with one another. These properties are determined by the compound’s ability to donate or accept protons (hydrogen ions) or to interact with hydroxide ions.

• Acids: These are substances that can donate protons (H⁺ ions) to other substances. They tend to taste sour and can conduct electricity in solution. An example of an acidic oxide is \( \mathrm{CrO}_{3} \), which reacts with bases to release protons, forming neutral products like salt and water.
• Bases: These substances accept protons or release hydroxide ions (OH⁻ ions) in solution. They usually have a slippery feel and a bitter taste. \( \mathrm{CrO} \) is an example of a basic oxide that reacts with acids to neutralize them.

Knowing these properties helps in predicting how substances are likely to react with each other. This understanding is key in fields ranging from industrial manufacturing to biochemical processes in the body.