Which Of The Following Solutions Would Have The Highest PH? Assume That They Are All 0.10 M In Acid At 25 ∘ C 25^{\circ} C 2 5 ∘ C . The Acid Is Followed By Its K A K_{a} K A ​ Value.A. H F , 3.5 × 10 − 4 HF, 3.5 \times 10^{-4} H F , 3.5 × 1 0 − 4 B. $HCN, 4.9 \times

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Which of the following solutions would have the highest pH?

In this article, we will explore the concept of pH and how it relates to the strength of an acid. We will examine four different acids, each with its own unique properties and strengths. By understanding the relationship between acid strength and pH, we can determine which solution would have the highest pH.

Understanding pH

pH is a measure of the concentration of hydrogen ions in a solution. It is a scale that ranges from 0 to 14, with 7 being neutral. A pH below 7 is considered acidic, while a pH above 7 is considered basic. The pH of a solution is determined by the concentration of hydrogen ions, which is in turn determined by the strength of the acid.

The Strength of an Acid

The strength of an acid is determined by its ability to donate hydrogen ions. Acids that are strong donors of hydrogen ions are considered strong acids, while those that are weak donors are considered weak acids. The strength of an acid is often measured by its acid dissociation constant, or Ka. A high Ka value indicates a strong acid, while a low Ka value indicates a weak acid.

The Four Acids

We are given four different acids, each with its own unique properties and strengths. The acids are:

  • HF (Hydrofluoric Acid): Ka = 3.5 x 10^-4
  • HCN (Hydrocyanic Acid): Ka = 4.9 x 10^-10
  • HCl (Hydrochloric Acid): Ka = 1.0 x 10^7
  • HNO3 (Nitric Acid): Ka = 1.0 x 10^7

Determining the pH of Each Solution

To determine the pH of each solution, we need to calculate the concentration of hydrogen ions in each solution. We can do this by using the acid dissociation equation:

Ka = [H+][A-] / [HA]

where [H+] is the concentration of hydrogen ions, [A-] is the concentration of conjugate base, and [HA] is the concentration of undissociated acid.

HF (Hydrofluoric Acid)

For HF, we can plug in the values we know into the acid dissociation equation:

3.5 x 10^-4 = [H+][F-] / [HF]

Since the concentration of HF is 0.10 M, we can assume that the concentration of undissociated HF is also 0.10 M. We can then rearrange the equation to solve for [H+]:

[H+] = sqrt(3.5 x 10^-4 x 0.10) = 1.9 x 10^-3 M

HCN (Hydrocyanic Acid)

For HCN, we can plug in the values we know into the acid dissociation equation:

4.9 x 10^-10 = [H+][CN-] / [HCN]

Since the concentration of HCN is 0.10 M, we can assume that the concentration of undissociated HCN is also 0.10 M. We can then rearrange the equation to solve for [H+]:

[H+] = sqrt(4.9 x 10^-10 x 0.10) = 2.2 x 10^-5 M

HCl (Hydrochloric Acid)

For HCl, we can plug in the values we know into the acid dissociation equation:

1.0 x 10^7 = [H+][Cl-] / [HCl]

Since the concentration of HCl is 0.10 M, we can assume that the concentration of undissociated HCl is also 0.10 M. We can then rearrange the equation to solve for [H+]:

[H+] = sqrt(1.0 x 10^7 x 0.10) = 3.2 x 10^-4 M

HNO3 (Nitric Acid)

For HNO3, we can plug in the values we know into the acid dissociation equation:

1.0 x 10^7 = [H+][NO3-] / [HNO3]

Since the concentration of HNO3 is 0.10 M, we can assume that the concentration of undissociated HNO3 is also 0.10 M. We can then rearrange the equation to solve for [H+]:

[H+] = sqrt(1.0 x 10^7 x 0.10) = 3.2 x 10^-4 M

Determining the pH of Each Solution

Now that we have calculated the concentration of hydrogen ions in each solution, we can determine the pH of each solution. We can do this by using the pH equation:

pH = -log[H+]

HF (Hydrofluoric Acid)

For HF, we can plug in the value of [H+] we calculated earlier into the pH equation:

pH = -log(1.9 x 10^-3) = 2.3

HCN (Hydrocyanic Acid)

For HCN, we can plug in the value of [H+] we calculated earlier into the pH equation:

pH = -log(2.2 x 10^-5) = 4.7

HCl (Hydrochloric Acid)

For HCl, we can plug in the value of [H+] we calculated earlier into the pH equation:

pH = -log(3.2 x 10^-4) = 3.5

HNO3 (Nitric Acid)

For HNO3, we can plug in the value of [H+] we calculated earlier into the pH equation:

pH = -log(3.2 x 10^-4) = 3.5

Conclusion

In conclusion, the solution with the highest pH is HCN (Hydrocyanic Acid), with a pH of 4.7. This is because HCN is a weak acid, and therefore has a low concentration of hydrogen ions. The other three acids, HF, HCl, and HNO3, are all strong acids, and therefore have a high concentration of hydrogen ions. As a result, their pH values are all lower than that of HCN.

References

  • Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.
  • Brown, T. E., LeMay, H. E., Bursten, B. E., & Murphy, C. (2012). Chemistry: The Central Science. Pearson Education.
  • Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2011). General chemistry: Principles and modern applications. Pearson Education.
    Frequently Asked Questions (FAQs) About pH and Acid Strength

In this article, we will answer some of the most frequently asked questions about pH and acid strength. Whether you are a student, a teacher, or simply someone interested in chemistry, these FAQs will provide you with a better understanding of the concepts.

Q: What is pH?

A: pH is a measure of the concentration of hydrogen ions in a solution. It is a scale that ranges from 0 to 14, with 7 being neutral. A pH below 7 is considered acidic, while a pH above 7 is considered basic.

Q: What is the difference between a strong acid and a weak acid?

A: A strong acid is an acid that completely dissociates in water, producing a high concentration of hydrogen ions. A weak acid, on the other hand, only partially dissociates in water, producing a low concentration of hydrogen ions.

Q: How do I determine the pH of a solution?

A: To determine the pH of a solution, you need to calculate the concentration of hydrogen ions in the solution. You can do this by using the acid dissociation equation:

Ka = [H+][A-] / [HA]

where [H+] is the concentration of hydrogen ions, [A-] is the concentration of conjugate base, and [HA] is the concentration of undissociated acid.

Q: What is the relationship between acid strength and pH?

A: The strength of an acid is directly related to its ability to donate hydrogen ions. Strong acids have a high ability to donate hydrogen ions, resulting in a low pH. Weak acids, on the other hand, have a low ability to donate hydrogen ions, resulting in a high pH.

Q: Can you give an example of a strong acid and a weak acid?

A: Yes, here are some examples:

  • HCl (Hydrochloric Acid): This is a strong acid, with a Ka value of 1.0 x 10^7. It completely dissociates in water, producing a high concentration of hydrogen ions.
  • HCN (Hydrocyanic Acid): This is a weak acid, with a Ka value of 4.9 x 10^-10. It only partially dissociates in water, producing a low concentration of hydrogen ions.

Q: How do I calculate the pH of a solution using the Ka value?

A: To calculate the pH of a solution using the Ka value, you need to follow these steps:

  1. Write down the acid dissociation equation for the acid in question.
  2. Plug in the values you know into the equation, including the Ka value and the concentration of the acid.
  3. Rearrange the equation to solve for [H+].
  4. Use the pH equation to calculate the pH of the solution.

Q: What is the significance of pH in everyday life?

A: pH is an important concept in everyday life, as it affects the taste, texture, and safety of many substances. For example:

  • Food and Drink: pH affects the taste and texture of food and drink. For example, a low pH can make a food taste sour, while a high pH can make it taste bitter.
  • Water Quality: pH affects the safety of water. For example, a low pH can make water acidic, which can be harmful to humans and animals.
  • Medicine: pH affects the effectiveness of many medicines. For example, a low pH can make a medicine more effective, while a high pH can make it less effective.

Q: Can you give some examples of acids and their pH values?

A: Yes, here are some examples:

  • HCl (Hydrochloric Acid): pH = 1.0
  • HNO3 (Nitric Acid): pH = 1.0
  • HCN (Hydrocyanic Acid): pH = 4.7
  • HF (Hydrofluoric Acid): pH = 2.3

Conclusion

In conclusion, pH and acid strength are important concepts in chemistry that affect many aspects of everyday life. By understanding the relationship between acid strength and pH, you can better appreciate the significance of pH in many different contexts. Whether you are a student, a teacher, or simply someone interested in chemistry, these FAQs will provide you with a better understanding of the concepts.