Which of the following pH range and colour 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 colourless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes colour is from 8.2 to 10.0.
In acidic medium, the pH of the solution is less than 7.0. Therefore, phenolphthalein will be in its colourless form. The correct answer is colourless.
Phenolphthalein is a weak acid with a pKa of 9.7. This means that it will only ionize to a small extent in acidic solutions. The equilibrium constant for the ionization of phenolphthalein is:
HIn + H2O <=> H3O+ + In-
where HIn is the protonated form of phenolphthalein and In- is the deprotonated form. The equilibrium constant for this reaction is very small, which means that only a small fraction of the phenolphthalein will be ionized in acidic solutions.
The colour change of phenolphthalein is due to a change in the molecular structure of the compound. In acidic solutions, the phenolphthalein molecule is in its protonated form. This form of the molecule is colourless. When the pH of the solution is increased, the phenolphthalein molecule loses a proton and becomes deprotonated. The deprotonated form of the molecule is pink.
Phenolphthalein is a very sensitive indicator. It can be used to detect even small changes in the pH of a solution. This makes it a valuable tool for acid-base titrations.
Which of the following pH range and colour 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 colourless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes colour is from 8.2 to 10.0.
- Colour change: Phenolphthalein is colourless in acidic solutions and pink in basic solutions.
- pH range: The pH range over which phenolphthalein changes colour is from 8.2 to 10.0.
- Chemical structure: Phenolphthalein is a weak acid with a pKa of 9.7.
- Ionization: Phenolphthalein only ionizes to a small extent in acidic solutions.
- Applications: Phenolphthalein is a valuable tool for acid-base titrations.
These five key aspects provide a comprehensive overview of phenolphthalein and its use as an indicator in acid-base titrations. Phenolphthalein is a versatile and sensitive indicator that can be used to detect even small changes in the pH of a solution.
Colour change
The colour change of phenolphthalein is a key aspect of its use as an indicator in acid-base titrations. This colour change is due to a change in the molecular structure of the compound. In acidic solutions, the phenolphthalein molecule is in its protonated form, which is colourless. When the pH of the solution is increased, the phenolphthalein molecule loses a proton and becomes deprotonated, which is pink.
The pH range over which phenolphthalein changes colour is from 8.2 to 10.0. This means that phenolphthalein can be used to detect even small changes in the pH of a solution. This makes it a valuable tool for acid-base titrations.
For example, phenolphthalein is often used to indicate the endpoint of a titration of a weak acid with a strong base. The titration is carried out by adding the strong base to the weak acid solution until the pH of the solution reaches 8.2. At this point, the phenolphthalein will turn pink, indicating that the equivalence point has been reached.
The colour change of phenolphthalein is a reversible process. If the pH of a solution that contains phenolphthalein is decreased, the phenolphthalein will turn colourless again.
pH range
The pH range over which phenolphthalein changes colour is a key aspect of its use as an indicator in acid-base titrations. This pH range determines the conditions under which phenolphthalein can be used to detect the endpoint of a titration.
- Facet 1: Acidic solutions
In acidic solutions, the pH is less than 7.0. Phenolphthalein is colourless in acidic solutions because it is in its protonated form. This means that phenolphthalein cannot be used to detect the endpoint of a titration in acidic solutions.
- Facet 2: Basic solutions
In basic solutions, the pH is greater than 7.0. Phenolphthalein is pink in basic solutions because it is in its deprotonated form. This means that phenolphthalein can be used to detect the endpoint of a titration in basic solutions.
- Facet 3: Neutral solutions
In neutral solutions, the pH is equal to 7.0. Phenolphthalein is colourless in neutral solutions because it is in its protonated form. This means that phenolphthalein cannot be used to detect the endpoint of a titration in neutral solutions.
- Facet 4: Applications
Phenolphthalein is a valuable tool for acid-base titrations. It is used to detect the endpoint of titrations in basic solutions. Phenolphthalein is also used as an indicator in other applications, such as the determination of the pH of a solution.
The pH range over which phenolphthalein changes colour is a critical factor in its use as an indicator. This pH range determines the conditions under which phenolphthalein can be used to detect the endpoint of a titration.
Chemical structure
The chemical structure of phenolphthalein is important in understanding how it functions as an indicator. Phenolphthalein is a weak acid, which means that it only partially dissociates in water. The pKa of phenolphthalein is 9.7, which means that it will only lose a proton in solutions with a pH greater than 9.7.
- Facet 1: Acidic solutions
In acidic solutions, the pH is less than 9.7. This means that phenolphthalein will not lose a proton and will remain in its protonated form. The protonated form of phenolphthalein is colourless.
- Facet 2: Basic solutions
In basic solutions, the pH is greater than 9.7. This means that phenolphthalein will lose a proton and will become deprotonated. The deprotonated form of phenolphthalein is pink.
- Facet 3: Colour change
The colour change of phenolphthalein is a reversible process. If the pH of a solution that contains phenolphthalein is decreased, the phenolphthalein will become colourless again.
The chemical structure of phenolphthalein is directly related to its behaviour as an indicator. The weak acidity of phenolphthalein means that it will only change colour in basic solutions. This makes phenolphthalein a valuable tool for acid-base titrations.
Ionization
The ionization of phenolphthalein is directly related to its colour change. In acidic solutions, phenolphthalein only ionizes to a small extent. This means that most of the phenolphthalein molecules are in their protonated form, which is colourless. As the pH of the solution increases, more and more phenolphthalein molecules ionize, resulting in a colour change from colourless to pink.
- Facet 1: Ionization constant
The ionization constant of phenolphthalein is 1.0 x 10^-10. This means that only a very small fraction of the phenolphthalein molecules will ionize in acidic solutions.
- Facet 2: pH range
The pH range over which phenolphthalein changes colour is from 8.2 to 10.0. This means that phenolphthalein is only a useful indicator in basic solutions.
- Facet 3: Applications
Phenolphthalein is a valuable tool for acid-base titrations. It is used to detect the endpoint of titrations in basic solutions.
The ionization of phenolphthalein is a key factor in its use as an indicator. The small ionization constant and the pH range over which phenolphthalein changes colour make it a valuable tool for acid-base titrations.
Applications
Phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations. It is colourless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes colour is from 8.2 to 10.0.
- Facet 1: Acid-base titrations
Acid-base titrations are a common laboratory technique used to determine the concentration of an unknown acid or base. Phenolphthalein is a valuable tool for acid-base titrations because it can be used to indicate the endpoint of the titration. The endpoint of the titration is the point at which the acid and base have been completely neutralized.
- Facet 2: Endpoint detection
Phenolphthalein is a very sensitive indicator, which means that it can be used to detect even small changes in the pH of a solution. This makes it a valuable tool for endpoint detection in acid-base titrations.
- Facet 3: Versatility
Phenolphthalein can be used in a wide variety of acid-base titrations. It is compatible with both strong and weak acids and bases.
- Facet 4: Low cost
Phenolphthalein is a relatively inexpensive indicator. This makes it a cost-effective option for acid-base titrations.
Phenolphthalein is a valuable tool for acid-base titrations. It is a sensitive, versatile, and low-cost indicator that can be used to detect the endpoint of a titration. This makes it a valuable tool for a variety of applications, including the determination of the concentration of an unknown acid or base.
FAQs about "which of the following ph range and colour 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 colourless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes colour is from 8.2 to 10.0.
Question 1: What is the pH range over which phenolphthalein changes colour?Answer: The pH range over which phenolphthalein changes colour is from 8.2 to 10.0. Question 2: What colour is phenolphthalein in acidic solutions?
Answer: Phenolphthalein is colourless in acidic solutions. Question 3: What colour is phenolphthalein in basic solutions?
Answer: Phenolphthalein is pink in basic solutions. Question 4: What is the chemical structure of phenolphthalein?
Answer: Phenolphthalein is a weak acid with a pKa of 9.7. Question 5: What are the applications of phenolphthalein?
Answer: Phenolphthalein is a valuable tool for acid-base titrations. It is used to detect the endpoint of titrations in basic solutions. Question 6: What are the limitations of phenolphthalein?
Answer: Phenolphthalein is not a suitable indicator for use in titrations of very weak acids or bases.
These are just a few of the most frequently asked questions about phenolphthalein. For more information, please consult a chemistry textbook or other reliable source.
Phenolphthalein is a versatile and sensitive indicator that can be used in a variety of applications. It is a valuable tool for chemists and other scientists.
Conclusion
Phenolphthalein is a chemical compound that is used as an indicator in acid-base titrations. It is colourless in acidic solutions and turns pink in basic solutions. The pH range over which phenolphthalein changes colour is from 8.2 to 10.0.
Phenolphthalein is a valuable tool for acid-base titrations. It is a sensitive and versatile indicator that can be used to detect the endpoint of titrations in basic solutions. However, it is important to note that phenolphthalein is not a suitable indicator for use in titrations of very weak acids or bases.
Overall, phenolphthalein is a valuable tool for chemists and other scientists. It is a versatile and inexpensive indicator that can be used in a variety of applications.
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