Top-Rated: Which PH Range And Color For Phenolphthalein In Acidic Medium?

14 Jun 2024
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Which of the following pH range and color is correct with respect to phenolphthalein indicator in acidic medium?

Phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations. It is colorless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes color is from 8.2 to 10.0. In acidic solutions, the phenolphthalein molecule is protonated, which means that it has a positive charge. This positive charge prevents the phenolphthalein molecule from interacting with water molecules, which makes it colorless. In basic solutions, the phenolphthalein molecule is deprotonated, which means that it has a negative charge. This negative charge allows the phenolphthalein molecule to interact with water molecules, which makes it pink.

The correct answer is 0 - 8.2 and colorless.

Phenolphthalein is a weak acid, and its dissociation constant (Ka) is 1.0 x 10^-10. This means that in acidic solutions, the concentration of the protonated form of phenolphthalein is much greater than the concentration of the deprotonated form. As the pH of the solution increases, the concentration of the deprotonated form of phenolphthalein increases, and the concentration of the protonated form decreases. At a pH of 8.2, the concentrations of the protonated and deprotonated forms of phenolphthalein are equal. This is the point at which the solution turns pink.

Phenolphthalein is a very sensitive indicator, and it can be used to detect even small changes in pH. This makes it a useful tool for a variety of applications, including acid-base titrations, water analysis, and soil testing.

Which of the following pH range and color is correct with respect to phenolphthalein indicator in acidic medium?

pH range: 8.2 to 10.0
Color in acidic medium: Colorless
Color in basic medium: Pink
Chemical structure: C20H14O4
Molecular weight: 318.33 g/mol

pH range

The pH range of 8.2 to 10.0 is significant in relation to phenolphthalein because it represents the range of pH values over which phenolphthalein changes color. Phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations. It is colorless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes color is narrow, which makes it a useful indicator for titrations involving weak acids and bases.

Facet 1: Acidic solutions
In acidic solutions, the pH is below 8.2. At this pH, phenolphthalein is protonated, which means that it has a positive charge. This positive charge prevents the phenolphthalein molecule from interacting with water molecules, which makes it colorless.
Facet 2: Basic solutions
In basic solutions, the pH is above 10.0. At this pH, phenolphthalein is deprotonated, which means that it has a negative charge. This negative charge allows the phenolphthalein molecule to interact with water molecules, which makes it pink.
Facet 3: Neutral solutions
At a pH of 8.2, phenolphthalein is neither protonated nor deprotonated. This means that it is in its neutral form, and it is colorless.
Facet 4: Applications
Phenolphthalein is a very sensitive indicator, and it can be used to detect even small changes in pH. This makes it a useful tool for a variety of applications, including acid-base titrations, water analysis, and soil testing.

In conclusion, the pH range of 8.2 to 10.0 is significant in relation to phenolphthalein because it represents the range of pH values over which phenolphthalein changes color. This makes phenolphthalein a useful indicator for titrations involving weak acids and bases.

Color in acidic medium

The connection between "Color in acidic medium: Colorless" and "which of the following pH range and color is correct with respect to phenolphthalein indicator in acidic medium?" is that phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations. It is colorless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes color is from 8.2 to 10.0.

Facet 1: Structure of phenolphthalein
Phenolphthalein is a weak acid, and its dissociation constant (Ka) is 1.0 x 10^-10. This means that in acidic solutions, the concentration of the protonated form of phenolphthalein is much greater than the concentration of the deprotonated form. The protonated form of phenolphthalein is colorless.
Facet 2: Acid-base reactions
In acidic solutions, the hydrogen ion concentration is high. This causes the protonated form of phenolphthalein to be the dominant species in solution. The protonated form of phenolphthalein is colorless. As the pH of the solution increases, the hydrogen ion concentration decreases. This causes the deprotonated form of phenolphthalein to become the dominant species in solution. The deprotonated form of phenolphthalein is pink.
Facet 3: Applications of phenolphthalein
Phenolphthalein is a very sensitive indicator, and it can be used to detect even small changes in pH. This makes it a useful tool for a variety of applications, including acid-base titrations, water analysis, and soil testing.

In conclusion, the connection between "Color in acidic medium: Colorless" and "which of the following pH range and color is correct with respect to phenolphthalein indicator in acidic medium?" is that phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations. It is colorless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes color is from 8.2 to 10.0.

Color in basic medium

The connection between "Color in basic medium: Pink" and "which of the following pH range and color is correct with respect to phenolphthalein indicator in acidic medium?" is that phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations. It is colorless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes color is from 8.2 to 10.0.

In basic solutions, the pH is above 10.0. At this pH, phenolphthalein is deprotonated, which means that it has a negative charge. This negative charge allows the phenolphthalein molecule to interact with water molecules, which makes it pink.

The color change of phenolphthalein is a useful tool for determining the pH of a solution. Phenolphthalein is often used in acid-base titrations to indicate the equivalence point, which is the point at which the acid and base have been completely neutralized. At the equivalence point, the pH of the solution will be 8.2, and the phenolphthalein will turn pink.

Phenolphthalein is a very sensitive indicator, and it can be used to detect even small changes in pH. This makes it a useful tool for a variety of applications, including:

Acid-base titrations
Water analysis
Soil testing

In conclusion, the connection between "Color in basic medium: Pink" and "which of the following pH range and color is correct with respect to phenolphthalein indicator in acidic medium?" is that phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations. It is colorless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes color is from 8.2 to 10.0.

Chemical structure

The chemical structure of phenolphthalein, C20H14O4, is directly related to its behavior as an acid-base indicator and its color change in acidic and basic solutions.

Facet 1: Phenolphthalein as a weak acid
Phenolphthalein is a weak acid, meaning that it only partially dissociates in water. The chemical structure of phenolphthalein includes a carboxylic acid group (-COOH), which is responsible for its acidic properties. In acidic solutions, the carboxylic acid group donates a hydrogen ion (H+), resulting in the formation of the protonated form of phenolphthalein, which is colorless.
Facet 2: Deprotonation and color change
In basic solutions, the hydroxide ion (OH-) concentration is higher than in acidic solutions. The hydroxide ions react with the protonated form of phenolphthalein, removing the hydrogen ion and causing the phenolphthalein to become deprotonated. Deprotonation results in a change in the chemical structure of phenolphthalein, leading to the formation of the phenolate ion, which is pink in color.
Facet 3: Equilibrium and pH range
The equilibrium between the protonated and deprotonated forms of phenolphthalein is influenced by the pH of the solution. At low pH values (acidic solutions), the protonated form predominates, and the solution remains colorless. As the pH increases (basic solutions), the concentration of hydroxide ions increases, favoring the deprotonated form, and the solution turns pink. The pH range over which phenolphthalein changes color is typically between 8.2 and 10.0.
Facet 4: Applications of phenolphthalein
Due to its distinct color change in response to pH changes, phenolphthalein is commonly used as an acid-base indicator in titrations and other chemical analyses. It is particularly useful for determining the equivalence point in acid-base titrations, where the solution turns pink when the acid and base have completely neutralized each other, indicating the endpoint of the titration.

In summary, the chemical structure of phenolphthalein, C20H14O4, plays a crucial role in its behavior as an acid-base indicator and its characteristic color change in acidic and basic solutions. Understanding the relationship between the chemical structure and the color change allows for the effective utilization of phenolphthalein in various applications, especially in acid-base titrations.

Molecular weight

The molecular weight of phenolphthalein, 318.33 g/mol, is directly related to its chemical composition, structure, and properties, which in turn influence its behavior as an acid-base indicator.

Facet 1: Chemical composition and structure
Phenolphthalein's molecular weight is a representation of the sum of the atomic weights of the elements that make up its molecular structure. The molecular formula of phenolphthalein, C20H14O4, indicates that each molecule is composed of 20 carbon atoms, 14 hydrogen atoms, and 4 oxygen atoms. This specific combination and arrangement of atoms contribute to the overall molecular weight of 318.33 g/mol.
Facet 2: Physical properties
The molecular weight of a compound is closely related to its physical properties, such as density, solubility, and melting point. Phenolphthalein's molecular weight influences its solubility in various solvents. Its relatively high molecular weight affects its solubility, making it less soluble in water compared to smaller molecules with lower molecular weights.
Facet 3: Chemical reactions and behavior
In the context of its use as an acid-base indicator, the molecular weight of phenolphthalein plays a role in determining its dissociation constant (Ka) and pKa value. The Ka value represents the equilibrium constant for the dissociation of phenolphthalein in water, and it is influenced by the molecular weight and structure of the compound. The pKa value, which is the negative logarithm of the Ka, is a measure of the acidity or alkalinity of a compound and is used to characterize the pH range over which phenolphthalein changes color.
Facet 4: Applications and implications
The molecular weight of phenolphthalein has implications for its applications and performance as an acid-base indicator. Its relatively high molecular weight contributes to its sensitivity and effectiveness within a specific pH range. Phenolphthalein is commonly used as an indicator in acid-base titrations and other analytical procedures where precise pH determination is required.

In summary, the molecular weight of phenolphthalein, 318.33 g/mol, is connected to its chemical composition, structure, physical properties, chemical behavior, and applications as an acid-base indicator. Understanding the molecular weight provides insights into the compound's characteristics and enables its effective utilization in various chemical and analytical contexts.

FAQs about Phenolphthalein Indicator in Acidic Medium

Phenolphthalein is a chemical compound often used as an indicator in acid-base titrations. It is colorless in acidic solutions and turns pink in basic solutions. Here are some frequently asked questions about phenolphthalein indicator in acidic medium:

Question 1: What is the pH range over which phenolphthalein changes color?

Phenolphthalein changes color over a pH range of 8.2 to 10.0. In acidic solutions (pH < 8.2), phenolphthalein remains colorless. As the pH increases, it turns pink at a pH of 8.2 and remains pink in basic solutions (pH > 8.2).

Question 2: Why is phenolphthalein colorless in acidic medium?

In acidic medium, phenolphthalein exists in its protonated form, which is colorless. The protonated form of phenolphthalein does not interact with water molecules, resulting in the absence of color.

Question 3: What causes phenolphthalein to turn pink in basic medium?

In basic medium, the hydrogen ion concentration is low, causing the protonated form of phenolphthalein to lose its proton. The resulting deprotonated form of phenolphthalein is pink and interacts with water molecules, giving the solution a pink color.

Question 4: What is the chemical structure of phenolphthalein?

Phenolphthalein has the chemical formula C20H14O4. Its molecular structure consists of two benzene rings connected by a central carbon atom and two hydroxyl groups (-OH) attached to the benzene rings.

Question 5: What are the applications of phenolphthalein as an indicator?

Phenolphthalein is commonly used as an indicator in acid-base titrations to determine the endpoint of the reaction. It is also used in various analytical procedures to detect the presence or absence of acids or bases.

Question 6: What are the limitations of using phenolphthalein as an indicator?

Phenolphthalein has a relatively narrow pH range (8.2-10.0) and may not be suitable for applications requiring a wider pH range. Additionally, phenolphthalein is not recommended for use in solutions containing strong oxidizing agents, as it can undergo oxidation and lose its ability to change color.

These FAQs provide a comprehensive overview of the behavior and applications of phenolphthalein indicator in acidic medium. Its unique color change properties make it a valuable tool for acid-base titrations and other analytical procedures.

Conclusion

Phenolphthalein is a widely used indicator in acid-base titrations due to its distinct color change properties. In acidic medium, phenolphthalein remains colorless because it exists in its protonated form. When the pH of the solution increases, phenolphthalein undergoes deprotonation, resulting in a visible pink color. This color change occurs within a specific pH range of 8.2 to 10.0.

Understanding the behavior of phenolphthalein indicator in acidic medium is essential for accurate and reliable acid-base titrations. Its unique color change properties make it a valuable tool for determining the endpoint of neutralization reactions and various analytical procedures. Phenolphthalein's limitations, such as its narrow pH range and sensitivity to oxidizing agents, should be considered when selecting an indicator for specific applications.

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