The Effect of Adding an Acid to Water

Oct 13, 2025 by miodeya.com 79 views

Introduction

In chemistry, acid-base reactions are crucial in understanding various chemical processes. When an acid is added to water, a new equilibrium is established, which affects the pH and pOH levels of the solution. In this article, we will explore the concept of pH and pOH, and discuss the system after the acid is added to water.

pH and pOH: A Brief Overview

pH is a measure of the concentration of hydrogen ions (H+) in a solution, while pOH is a measure of the concentration of hydroxide ions (OH-) in a solution. The pH scale ranges from 0 to 14, with a pH of 7 being neutral. A pH less than 7 is acidic, while a pH greater than 7 is basic.

The relationship between pH and pOH is given by the equation:

pH + pOH = 14

The Effect of Adding an Acid to Water

When an acid is added to water, it dissociates into hydrogen ions (H+) and the conjugate base of the acid. This increases the concentration of hydrogen ions in the solution, which in turn decreases the pH.

System After the Acid is Added

After the acid is added to water, the system is no longer at equilibrium. The acid dissociates into hydrogen ions and the conjugate base, which increases the concentration of hydrogen ions in the solution.

The correct answer is C. pH > pOH.

Explanation

When an acid is added to water, the concentration of hydrogen ions (H+) increases, which decreases the pH. However, the concentration of hydroxide ions (OH-) also increases, which increases the pOH.

Since pH + pOH = 14, if the pH decreases, the pOH must increase to maintain the equilibrium. Therefore, after the acid is added to water, the system is characterized by a pH greater than pOH.

Example

Consider a solution of hydrochloric acid (HCl) in water. When HCl is added to water, it dissociates into hydrogen ions (H+) and chloride ions (Cl-).

HCl (aq) → H+ (aq) + Cl- (aq)

The concentration of hydrogen ions (H+) increases, which decreases the pH. However, the concentration of hydroxide ions (OH-) also increases, which increases the pOH.

Conclusion

In conclusion, when an acid is added to water, a new equilibrium is established, which affects the pH and pOH levels of the solution. The correct answer is C. pH > pOH, as the system is characterized by a pH greater than pOH after the acid is added to water.

Key Takeaways

pH is a measure of the concentration of hydrogen ions (H+) in a solution.
pOH is a measure of the concentration of hydroxide ions (OH-) in a solution.
The relationship between pH and pOH is given by the equation: pH + pOH = 14.
When an acid is added to water, the concentration of hydrogen ions (H+) increases, which decreases the pH.
The concentration of hydroxide ions (OH-) also increases, which increases the pOH.
The system is characterized by a pH greater than pOH after the acid is added to water.

References

Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.
Brown, T. E., & LeMay, H. E. (2014). Chemistry: The Central Science. Pearson Education.

Introduction

In our previous article, we explored the concept of pH and pOH, and discussed the system after the acid is added to water. In this article, we will answer some frequently asked questions related to pH and equilibrium in acid-base reactions.

Q&A

Q: What is the pH of a solution with a high concentration of hydrogen ions?

A: The pH of a solution with a high concentration of hydrogen ions is low. In fact, the pH is inversely proportional to the concentration of hydrogen ions.

Q: What is the pOH of a solution with a low concentration of hydroxide ions?

A: The pOH of a solution with a low concentration of hydroxide ions is high. In fact, the pOH is inversely proportional to the concentration of hydroxide ions.

Q: What is the relationship between pH and pOH?

A: The relationship between pH and pOH is given by the equation: pH + pOH = 14.

Q: What happens to the pH of a solution when an acid is added?

A: When an acid is added to a solution, the concentration of hydrogen ions increases, which decreases the pH.

Q: What happens to the pOH of a solution when an acid is added?

A: When an acid is added to a solution, the concentration of hydroxide ions increases, which increases the pOH.

Q: Can the pH of a solution be greater than 14?

A: No, the pH of a solution cannot be greater than 14. The pH scale ranges from 0 to 14, with a pH of 7 being neutral.

Q: Can the pOH of a solution be less than 0?

A: No, the pOH of a solution cannot be less than 0. The pOH scale ranges from 0 to 14, with a pOH of 7 being neutral.

Q: What is the pH of a solution with a pH greater than 7?

A: A solution with a pH greater than 7 is basic.

Q: What is the pH of a solution with a pH less than 7?

A: A solution with a pH less than 7 is acidic.

Q: Can a solution have a pH of exactly 7?

A: Yes, a solution with a pH of exactly 7 is neutral.

Q: What is the pH of a solution with a high concentration of hydroxide ions?

A: The pH of a solution with a high concentration of hydroxide ions is high. In fact, the pH is inversely proportional to the concentration of hydroxide ions.

Q: What is the pOH of a solution with a low concentration of hydrogen ions?

A: The pOH of a solution with a low concentration of hydrogen ions is low. In fact, the pOH is inversely proportional to the concentration of hydrogen ions.

Conclusion

In conclusion, pH and pOH are important concepts in chemistry that help us understand the properties of solutions. By answering these frequently asked questions, we hope to have provided a better understanding of pH and equilibrium in acid-base reactions.

Key Takeaways

pH is a measure of the concentration of hydrogen ions (H+) in a solution.
pOH is a measure of the concentration of hydroxide ions (OH-) in a solution.
The relationship between pH and pOH is given by the equation: pH + pOH = 14.
When an acid is added to a solution, the concentration of hydrogen ions increases, which decreases the pH.
The concentration of hydroxide ions increases, which increases the pOH.
A solution with a pH greater than 7 is basic.
A solution with a pH less than 7 is acidic.
A solution with a pH of exactly 7 is neutral.

References

Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.
Brown, T. E., & LeMay, H. E. (2014). Chemistry: The Central Science. Pearson Education.