Why does buffer resist changes in ph

The two reactions that would take place are:. The pH of this buffer could be calculated by using the Henderson-Hasselbalch equation, or by working through a reaction table ICE to calculate equilibrium concentrations of the species in the buffer. We will do both sets of calculations. Initial 1. Equilibrium 1. Using the Henderson-Hasselbalch equation gives:.

What is the effect of adding of 0. The strong acid, HCl would dissociate completely in water:. The new concentration would be:. The equilibrium would then be re-established:. There is a small change in pH, from 4. This same amount of HCl added to water shows a much bigger effect. For example, we could make a solution that is 0. Yet, in real life, the chloride ion is usually reluctant to accept a proton and turn into its conjugate acid, HCl.

Because of this behavior, strong acids and their conjugate bases do not usually form buffer solutions. So too do strong bases. As a result, buffer solutions usually consist of a mixture of weak acids and their conjugate bases and weak bases and their conjugate acids. Here is an example of a weak acid—acetic acid with its conjugate base—acetate ion. Together, they can form a buffer:. To understand how buffer solution resist changes in pH, we must first consider the dissociation of weak acid in water.

However, since HA is a weak acid, only some of its molecules will dissociate. As a result, we can write the following equations to describe the dissociation of weak acid in water:. The further addition of an acid or base to the buffer will change its pH quickly. Thus the breaking of the buffer is its capacity, or in other words, it is the amount of acid or base, a buffer can absorb before breaking its capacity. It is to be noted that a solution with a weak base has a higher buffer capacity for addition of a strong acid and a solution of weak acid has higher buffer capacity for the addition of strong base.

Here it is to be noted that the stronger the acid or base, the weaker the conjugate, and the weaker the acid or base, the stronger the conjugate. What is a Buffer and how does it work? Typically, they require a college degree with at least a year of special training in blood biology and chemistry.

This page was constructed from content via the following contributor s and edited topically or extensively by the LibreTexts development team to meet platform style, presentation, and quality:. Learning Objective Define buffer and describe how it reacts with an acid or a base.

Assume that all are aqueous solutions. The combination of these two solutes would make a buffer solution. Hydrochloric acid HCl is a strong acid, not a weak acid, so the combination of these two solutes would not make a buffer solution. Because it is not on our list of strong bases, we can assume that it is a weak base. The compound CH 3 NH 3 Cl is a salt made from that weak base, so the combination of these two solutes would make a buffer solution.

The combination of these two solutes would not make a buffer solution. Answer b No. Need a weak acid or base and a salt of its conjugate base or acid.