The key difference between pH and buffer is that the pH is a logarithmic scale whereas a buffer is an aqueous solution.
We can use the pH of a liquid to determine whether it is an acid or a base. It also is helpful in determining the buffering capacity of a buffer. A buffer solution contains a mixture of a weak acid and its conjugate base, or vice versa. Therefore, it tends to resist changes in the pH of the solution.
CONTENTS
1. Overview and Key Difference
2. What is pH
3. What is Buffer
4. Side by Side Comparison – pH vs Buffer in Tabular Form
5. Summary
What is pH?
pH is a logarithmic scale that we use to determine the acidity or the basicity of an aqueous solution. It is the negative base 10 logarithm of the hydrogen ion concentration measured in the unit mol/L. If we express it more precisely, we should use the activity of hydrogen ions instead of the concentration. The pH scale has numbers from 0 to 14. Solutions having a pH less than 7 are acidic and if the pH is higher than 7, it is a basic solution. The pH 7 indicates a neutral solution, i.e. pure water.
Figure 01: pH of Different Components
The equation for the determination of pH is as follows:
pH = log10(aH+)
Here “a” is the activity of hydrogen ions (H+). pH value depends on the temperature of the solution as the temperature can alter the activity of a chemical species. Therefore, when giving the pH of an aqueous solution, we should indicate the temperature at which the pH measured precisely. We use the pH scale in order to determine the quality of water, soil, etc.
What is Buffer?
A buffer is an aqueous solution that tends to resist the change in pH. This solution contains a mixture of a weak acid and its conjugate base or vice versa. The pH of these solutions changes slightly upon addition of either a strong acid or a strong base.
The weak acid (or base) and its conjugate base (or conjugate acid) are in equilibrium with each other. Then if we add some strong acid to this system, the equilibrium shifts towards the acid, and it forms more acid using the hydrogen ions released from the added strong acid. Therefore, although we expect an increase of the hydrogen ions upon addition of the strong acid, it doesn’t increase that much. Similarly, if we add a strong base, the hydrogen ion concentration decreases by less than the amount expected for the quantity of alkali added. We can measure this resistance to pH changes as the buffer capacity. The buffer capacity measures the resistance of a buffer to pH change on the addition of OH– ions (a base). We can give it in an equation as follows:
β = dn/d(pH)
where β is buffer capacity, dn is an infinitesimal amount of added base, and d(pH) is the resulting infinitesimal change in pH.
When considering the applications of buffers, these solutions are necessary to keep the correct pH for enzymatic activity in organisms. Moreover, these are used in industries in fermentation processes, setting the correct conditions for dyes, in chemical analysis, calibrating pH meters, etc.
What is the Difference Between pH and Buffer?
pH is a logarithmic scale that we use to determine the acidity or the basicity of an aqueous solution whereas, a buffer is an aqueous solution that tends to resist the change in pH. This is the key difference between pH and buffer. Moreover, the pH is a very important scale in chemistry. We can measure the pH of a solution using a pH meter or via experimental methods. Furthermore, we use the pH scale in order to determine the quality of water, soil, etc. On the other hand, the use of buffer solutions is to maintains the correct pH for enzymatic activity, in fermentation processes in industries, in setting the correct conditions for dyes, in chemical analysis, calibrating pH meters, etc. We measure the buffer capacity of a buffer using chemical analysis.
Summary – pH vs Buffer
pH is a fundamental scale that we use in chemistry to measure the acidity r basicity of a solution. Buffers are chemical solutions that can resist the changes in pH. Therefore, the difference between pH and buffer is that the pH is a logarithmic scale whereas a buffer is an aqueous solution.
Reference:
1. “PH.” Wikipedia, Wikimedia Foundation, 3 Aug. 2018. Available here
2. “Buffer Solution.” Wikipedia, Wikimedia Foundation, 27 July 2018. Available here
Image Courtesy:
1.”PH Scale”By Edward Stevens – Own work, (CC BY 3.0) via Commons Wikimedia