Which Of These Statements Best Explains Why Pure Water Has A PH Of 7?A. Pure Water Contains Only H 2 O H_2O H 2 ​ O Molecules, But PH Is Based On The Concentration Of H 3 O + H_3O^+ H 3 ​ O + Ions.B. Each Molecule Of Water Can Dissociate To Form $7

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Understanding the pH of Pure Water: A Comprehensive Analysis

Introduction

The pH scale is a fundamental concept in chemistry that measures the acidity or basicity of a solution. Pure water, in particular, has a pH of 7, which is considered neutral. However, the reasons behind this pH value are often misunderstood. In this article, we will delve into the explanations provided by two statements and determine which one best explains why pure water has a pH of 7.

Statement A: pH is Based on the Concentration of H3O+H_3O^+ Ions

The pH Scale and the Concentration of H3O+H_3O^+ Ions

The pH scale is defined as the negative logarithm of the concentration of hydrogen ions (H+H^+) in a solution. In the case of pure water, the pH is 7, which means that the concentration of H+H^+ ions is 10−710^{-7} moles per liter. However, statement A claims that pure water contains only H2OH_2O molecules, but pH is based on the concentration of H3O+H_3O^+ ions.

The Role of H3O+H_3O^+ Ions in Pure Water

In pure water, water molecules (H2OH_2O) can dissociate to form hydronium ions (H3O+H_3O^+) and hydroxide ions (OH−OH^-). This process is known as self-ionization, and it occurs to a very small extent. The concentration of H3O+H_3O^+ ions in pure water is indeed 10−710^{-7} moles per liter, which is the same as the concentration of H+H^+ ions.

Why pH is Based on the Concentration of H+H^+ Ions, Not H3O+H_3O^+ Ions

Although the concentration of H3O+H_3O^+ ions in pure water is 10−710^{-7} moles per liter, the pH scale is based on the concentration of H+H^+ ions, not H3O+H_3O^+ ions. This is because the H3O+H_3O^+ ion is a hydrated proton, and its concentration is equivalent to the concentration of H+H^+ ions. Therefore, statement A is partially correct, but it does not fully explain why pure water has a pH of 7.

Statement B: Each Molecule of Water Can Dissociate to Form $7

The Self-Ionization of Water

Statement B claims that each molecule of water can dissociate to form 77 ions. However, this statement is incorrect. The self-ionization of water is a very small process, and each molecule of water can dissociate to form only one H3O+H_3O^+ ion and one OH−OH^- ion.

The Concentration of H3O+H_3O^+ Ions in Pure Water

As mentioned earlier, the concentration of H3O+H_3O^+ ions in pure water is 10−710^{-7} moles per liter. This concentration is a result of the self-ionization of water, but it is not due to the dissociation of each molecule of water to form 77 ions.

Why Pure Water Has a pH of 7

Pure water has a pH of 7 because the concentration of H+H^+ ions is 10−710^{-7} moles per liter. This concentration is a result of the self-ionization of water, which occurs to a very small extent. The pH scale is based on the concentration of H+H^+ ions, not H3O+H_3O^+ ions, so statement A is partially correct, but it does not fully explain why pure water has a pH of 7.

Conclusion

In conclusion, statement A is partially correct, but it does not fully explain why pure water has a pH of 7. The pH scale is based on the concentration of H+H^+ ions, not H3O+H_3O^+ ions. Statement B is incorrect, as each molecule of water can dissociate to form only one H3O+H_3O^+ ion and one OH−OH^- ion. The correct explanation for the pH of pure water is that the concentration of H+H^+ ions is 10−710^{-7} moles per liter, which is a result of the self-ionization of water.

References

  • Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
  • Brown, T. E., & LeMay, H. E. (2012). Chemistry: The Central Science (12th ed.). Pearson Education.
  • Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2016). General chemistry: Principles and modern applications (11th ed.). Pearson Education.

Further Reading

  • For a more detailed explanation of the pH scale and the concentration of H+H^+ ions in pure water, see the article "The pH Scale: A Comprehensive Analysis" by [Author's Name].
  • For a discussion on the self-ionization of water, see the article "The Self-Ionization of Water: A Review" by [Author's Name].
    Frequently Asked Questions: Understanding the pH of Pure Water

Introduction

The pH of pure water is a fundamental concept in chemistry that has been extensively studied and debated. In our previous article, we explored the reasons behind the pH of pure water and determined that the concentration of H+H^+ ions is 10−710^{-7} moles per liter. In this article, we will address some of the most frequently asked questions related to the pH of pure water.

Q: What is the pH of pure water?

A: The pH of pure water is 7, which is considered neutral.

Q: Why does pure water have a pH of 7?

A: Pure water has a pH of 7 because the concentration of H+H^+ ions is 10−710^{-7} moles per liter. This concentration is a result of the self-ionization of water, which occurs to a very small extent.

Q: What is the self-ionization of water?

A: The self-ionization of water is a process in which water molecules (H2OH_2O) dissociate to form hydronium ions (H3O+H_3O^+) and hydroxide ions (OH−OH^-). This process occurs to a very small extent and is responsible for the pH of pure water.

Q: Why is the pH scale based on the concentration of H+H^+ ions?

A: The pH scale is based on the concentration of H+H^+ ions because the concentration of H+H^+ ions is equivalent to the concentration of H3O+H_3O^+ ions. The H3O+H_3O^+ ion is a hydrated proton, and its concentration is used to determine the pH of a solution.

Q: Can each molecule of water dissociate to form 77 ions?

A: No, each molecule of water can dissociate to form only one H3O+H_3O^+ ion and one OH−OH^- ion. The statement that each molecule of water can dissociate to form 77 ions is incorrect.

Q: What is the relationship between the pH of pure water and the concentration of H+H^+ ions?

A: The pH of pure water is directly related to the concentration of H+H^+ ions. The pH scale is based on the negative logarithm of the concentration of H+H^+ ions, so a higher concentration of H+H^+ ions results in a lower pH, and a lower concentration of H+H^+ ions results in a higher pH.

Q: Can the pH of pure water be affected by external factors?

A: Yes, the pH of pure water can be affected by external factors such as temperature, pressure, and the presence of impurities. However, the pH of pure water is generally considered to be 7 at standard temperature and pressure.

Q: What are some common applications of the pH of pure water?

A: The pH of pure water has many practical applications, including:

  • Water treatment: The pH of water is an important factor in water treatment processes, as it can affect the removal of impurities and the formation of scale.
  • Industrial processes: The pH of water is often used as a control parameter in industrial processes, such as chemical reactions and material processing.
  • Environmental monitoring: The pH of water is an important indicator of water quality and can be used to monitor the health of aquatic ecosystems.

Conclusion

In conclusion, the pH of pure water is a fundamental concept in chemistry that has been extensively studied and debated. We hope that this article has provided a clear and concise explanation of the pH of pure water and its relationship to the concentration of H+H^+ ions. If you have any further questions or would like to learn more about the pH of pure water, please do not hesitate to contact us.

References

  • Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
  • Brown, T. E., & LeMay, H. E. (2012). Chemistry: The Central Science (12th ed.). Pearson Education.
  • Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2016). General chemistry: Principles and modern applications (11th ed.). Pearson Education.

Further Reading

  • For a more detailed explanation of the pH scale and the concentration of H+H^+ ions in pure water, see the article "The pH Scale: A Comprehensive Analysis" by [Author's Name].
  • For a discussion on the self-ionization of water, see the article "The Self-Ionization of Water: A Review" by [Author's Name].