A Dye Known As Bromothymol Blue Appears Yellow Under Some Conditions And Blue Under Others, As Shown In The Following Equation:$\[ HB(aq) \leftrightarrow H^{+}(aq) + B^{-}(aq) \\] Yellow → BlueWhich Chemical Would Contribute A Common Ion If
A Dye Known as Bromothymol Blue: Understanding the Equilibrium of a Weak Acid
Bromothymol blue is a pH indicator dye that exhibits a unique property - it appears yellow under certain conditions and blue under others. This phenomenon can be explained by the equilibrium of a weak acid, which is a crucial concept in chemistry. In this article, we will delve into the world of acid-base chemistry and explore the equilibrium of a weak acid, specifically bromothymol blue.
The Equilibrium of a Weak Acid
A weak acid is an acid that does not completely dissociate in water, resulting in a mixture of the acid and its conjugate base. The equilibrium of a weak acid can be represented by the following equation:
In this equation, HB represents the weak acid, H+ represents the hydrogen ion, and B- represents the conjugate base.
The pH Scale
The pH scale is a measure of the concentration of hydrogen ions in a solution. It ranges from 0 to 14, with a pH of 7 being neutral. A pH below 7 is acidic, while a pH above 7 is basic.
Bromothymol Blue: A pH Indicator Dye
Bromothymol blue is a pH indicator dye that changes color in response to changes in pH. At a pH below 7, bromothymol blue appears yellow, while at a pH above 7, it appears blue. This color change is due to the equilibrium of the weak acid, which is affected by the concentration of hydrogen ions.
The Common Ion Effect
The common ion effect is a phenomenon that occurs when a solution contains a common ion, which is an ion that is present in both the acid and its conjugate base. In the case of bromothymol blue, the common ion is the hydrogen ion (H+).
Which Chemical Would Contribute a Common Ion?
To determine which chemical would contribute a common ion, we need to consider the equilibrium of the weak acid. In this case, the weak acid is bromothymol blue, which can be represented by the following equation:
If a chemical is added to the solution that contains a common ion, it will affect the equilibrium of the weak acid. In this case, the common ion is the hydrogen ion (H+).
Chemicals That Contribute a Common Ion
There are several chemicals that can contribute a common ion to the solution. Some of these chemicals include:
- Hydrochloric acid (HCl): Hydrochloric acid is a strong acid that completely dissociates in water, resulting in a high concentration of hydrogen ions. If hydrochloric acid is added to the solution, it will contribute a common ion and affect the equilibrium of the weak acid.
- Sodium hydroxide (NaOH): Sodium hydroxide is a strong base that completely dissociates in water, resulting in a high concentration of hydroxide ions. If sodium hydroxide is added to the solution, it will contribute a common ion and affect the equilibrium of the weak acid.
- Ammonium chloride (NH4Cl): Ammonium chloride is a salt that contains a common ion, which is the ammonium ion (NH4+). If ammonium chloride is added to the solution, it will contribute a common ion and affect the equilibrium of the weak acid.
In conclusion, bromothymol blue is a pH indicator dye that exhibits a unique property - it appears yellow under certain conditions and blue under others. This phenomenon can be explained by the equilibrium of a weak acid, which is a crucial concept in chemistry. The common ion effect is a phenomenon that occurs when a solution contains a common ion, which is an ion that is present in both the acid and its conjugate base. In the case of bromothymol blue, the common ion is the hydrogen ion (H+). By understanding the equilibrium of a weak acid and the common ion effect, we can determine which chemical would contribute a common ion to the solution.
- Klotz, I. M. (1964). Chemical Thermodynamics. W.A. Benjamin, Inc.
- Perrin, D. D. (1969). Ionization Constants of Inorganic Acids and Bases in Aqueous Solution. Pergamon Press.
- Skoog, D. A., West, D. M., Holler, F. J., & Crouch, S. R. (2007). Fundamentals of Analytical Chemistry. Thomson Brooks/Cole.
A Dye Known as Bromothymol Blue: Understanding the Equilibrium of a Weak Acid
Q: What is bromothymol blue?
A: Bromothymol blue is a pH indicator dye that exhibits a unique property - it appears yellow under certain conditions and blue under others.
Q: What is the pH range of bromothymol blue?
A: The pH range of bromothymol blue is between 6.0 and 7.6. At a pH below 6.0, it appears yellow, while at a pH above 7.6, it appears blue.
Q: What is the equilibrium of a weak acid?
A: The equilibrium of a weak acid is a chemical reaction in which the acid dissociates into its conjugate base and hydrogen ions. The equilibrium can be represented by the following equation:
Q: What is the common ion effect?
A: The common ion effect is a phenomenon that occurs when a solution contains a common ion, which is an ion that is present in both the acid and its conjugate base.
Q: Which chemical would contribute a common ion to the solution?
A: The chemical that would contribute a common ion to the solution is a chemical that contains a common ion, such as hydrochloric acid (HCl), sodium hydroxide (NaOH), or ammonium chloride (NH4Cl).
Q: What is the effect of adding a common ion to the solution?
A: Adding a common ion to the solution will affect the equilibrium of the weak acid. The common ion will shift the equilibrium to the left, resulting in a decrease in the concentration of hydrogen ions.
Q: How can the pH of a solution be determined using bromothymol blue?
A: The pH of a solution can be determined using bromothymol blue by observing the color change of the dye. At a pH below 6.0, the dye appears yellow, while at a pH above 7.6, it appears blue.
Q: What are some common applications of bromothymol blue?
A: Bromothymol blue is commonly used in chemistry laboratories to determine the pH of a solution. It is also used in biological research to study the effects of pH on cellular processes.
Q: Is bromothymol blue a strong acid or a weak acid?
A: Bromothymol blue is a weak acid. It does not completely dissociate in water, resulting in a mixture of the acid and its conjugate base.
Q: Can bromothymol blue be used to determine the pH of a solution that contains a common ion?
A: Yes, bromothymol blue can be used to determine the pH of a solution that contains a common ion. However, the presence of a common ion will affect the equilibrium of the weak acid, resulting in a shift in the pH of the solution.
Q: What are some common mistakes to avoid when using bromothymol blue?
A: Some common mistakes to avoid when using bromothymol blue include:
- Not using a sufficient amount of bromothymol blue to accurately determine the pH of the solution.
- Not allowing the solution to equilibrate before observing the color change of the dye.
- Not considering the effects of a common ion on the equilibrium of the weak acid.
In conclusion, bromothymol blue is a pH indicator dye that exhibits a unique property - it appears yellow under certain conditions and blue under others. The equilibrium of a weak acid and the common ion effect are crucial concepts in understanding the behavior of bromothymol blue. By understanding these concepts, we can determine the pH of a solution using bromothymol blue and avoid common mistakes.