177. A 1 M Tris-HCI (pH 8.0) solution was diluted 10 fold. What will be the pH of the resulting
solution?
A. 8.0
B. 7.0
C. 0.08
D. 0.8

Introduction

Tris-HCl (tris(hydroxymethyl)aminomethane hydrochloride) is a common buffering agent used in biological and biochemical applications to maintain stable pH levels in solutions. Its effectiveness as a buffer comes from its ability to resist changes in pH, even when it is diluted or subjected to changes in temperature or concentration. In this article, we will explore the effect of diluting a 1 M Tris-HCl solution (pH 8.0) by 10 fold and how the pH of the resulting solution is affected.

Understanding pH and Buffer Solutions

pH is a measure of the acidity or alkalinity of a solution, defined as the negative logarithm of the hydrogen ion concentration. For buffer solutions like Tris-HCl, the pH is determined by the concentration of the weak acid (Tris-HCl) and its conjugate base. Tris-HCl is particularly effective in maintaining a stable pH range of around 7-9, which is why it is commonly used in laboratory experiments that require a neutral to slightly basic environment.

Dilution of a buffer solution can affect its ability to resist changes in pH, but the pH itself is generally stable if the dilution is not extreme. A 10-fold dilution of the Tris-HCl solution in this case is unlikely to change the pH drastically, especially since Tris is a good buffer in the pH range of 7-9.

Impact of 10-Fold Dilution on pH

When a 1 M Tris-HCl solution (pH 8.0) is diluted by 10 fold, the concentration of the buffer components decreases, but the pH remains largely unchanged because the buffer capacity of Tris is not overwhelmed by the dilution. The Tris buffer will continue to function effectively, maintaining a stable pH around its optimal buffering range, typically near 8.0.

Therefore, after the 10-fold dilution, the pH of the resulting solution will still be approximately 8.0.

Conclusion

The pH of the resulting 10-fold diluted Tris-HCl solution will remain very close to the original pH of 8.0, as Tris is an effective buffer. The correct answer is:

A. 8.0