Table of Contents
What is meant by Henderson-Hasselbalch equation?
The HendersonHasselbalch equation relates the pH of a solution containing a mixture of the two components to the acid dissociation constant, Ka, and the concentrations of the species in solution. To derive the equation a number of simplifying assumptions have to be made.
How do you calculate Henderson-Hasselbalch equation?
What is Henderson-Hasselbalch equation and its uses?
The Henderson-Hasselbalch equation is useful for estimating the pH of a buffer solution and finding the equilibrium pH in an acid-base reaction. … The equation can be used to determine the amount of acid and conjugate base needed to make a buffer solution of a certain pH.
How is the Henderson equation derived?
How does the Henderson-Hasselbalch equation aid in buffer design?
In electrophoresis, the buffer is able to maintain a relatively constant pH as long as neither the acid nor the base becomes exhausted. The Henderson-Hasselbalch equation gives information in addition to how the pH is a function of the relative predominance of acid base forms of a buffer.
What assumptions does the Henderson Hasselbalch equation make?
Assumptions for the Henderson-Hasselbalch Equation Use the approximation only when the following conditions are met: 1 < log ([A]/[HA]) < 1. Molarity of buffers should be 100x greater than that of the acid ionization constant Ka. Only use strong acids or strong bases if the pKa values fall between 5 and 9.
What are the applications of the Henderson Hasselbalch equation in pharmaceutical analysis?
The Henderson-Hasselbalch equation can be utilized to calculate the pKa of a molecule using the chemical moiety present in the solution, pH of the solution and by measuring (using some other method) the ratio of its ionized and unionized forms.
When can the Henderson Hasselbalch equation be used and when does it fail?
This equation will give poor or inaccurate results if there are strong acids or bases. pKa values between 5 and 9 will give good approximations, but when we are out of this range there is a strong chance that the pH value will be incorrect.
Where is the Henderson-Hasselbalch equation derived?
The Henderson-Hasselbalch equation can be derived from the equilibrium constant expression for the dissociation of a weak acid. Consider the dissociation of the acid HA in water H2O [ 2 – 6 ].
How does the Henderson-Hasselbalch equation explain the shape of a titration curve?
The Henderson-Hasselbalch equation also describes the characteristic shape of the titration curve of any weak acid such as acetic acid, phosphoric acid, or any amino acid. … This equimolar solution of a weak acid and its conjugate base will resist the change in pH by donating or taking up the H ions.
What are the limitations of the Henderson Hasselbalch equation?
Limitations. The most critical assumption of this equation is that the concentration of acid and its conjugate base will remain the same during the equilibrium. The significance of hydrolysis of water and its effect on the pH of the overall solution is neglected.
What PKA is used for Henderson Hasselbalch?
You must use pKa2 .
Which of the following approximations is the Henderson Hasselbalch equation based on?
The Henderson-Hasselbalch equation makes use of the approximations [A-] = [base]initial and [HA] = [acid]initial.
Is Henderson-Hasselbalch an approximation?
According to Henderson-Hasselbach equation, when the concentrations of the acid and the conjugate base are the same, i.e, when the acid is 50% dissociated, the pH of the solution is equal to the pKa of the acid. … The Henderson-Hasselbalch equation (Equation 9) is an approximation, with a certain region of validity.
Can you use pKb in Henderson-Hasselbalch equation?
You can rewrite the Henderson-Hasselbalch equation for bases: pOH = pKb + log ([B+]/[BOH]), where pKb is the base’s dissociation constant, [B+] stands for the concentration of a base’s conjugate acid and [BOH] is the concentration of the base. … 137 – log[HA].
How do you use Henderson-Hasselbalch?
The formula for the HendersonHasselbalch equation is: pH=pKa+log([A][HA]) pH = p K a + log ( [ A ] [ HA ] ) , where pH is the concentration of [H+], pKa is the acid dissociation constant, and [A] and [HA] are concentrations of the conjugate base and starting acid.