EKG said:Homework Statement
What is the concentration of acetic acid in 250mL of a 100mM acetate buffer at pH 4.76?
Homework Equations
Henderson Hasselback
The Attempt at a Solution
I used the Henderson Hasselback equation. plugged in 4.76 for pKa. plugged in .025 for the concentration of A-. plugged in 4.76 for pH. Solved and got 25mM. The answer is supposed to be 50mM. Would appreciate the help, thanks.
The Henderson Hasselback equation is a mathematical formula used to calculate the pH of a solution containing a weak acid and its conjugate base. It takes into account the acid dissociation constant, the initial concentrations of the acid and its conjugate base, and the ionic strength of the solution.
The Henderson Hasselback equation is important because it allows scientists to estimate the pH of a solution without having to directly measure it. This is especially useful in laboratory experiments and in various industries where precise control of pH is necessary.
To calculate the acetic acid concentration, or any other weak acid concentration, using the Henderson Hasselback equation, you will need to know the pKa value of the acid, the initial concentrations of the acid and its conjugate base, and the ionic strength of the solution. Plug these values into the equation: pH = pKa + log([conjugate base]/[acid]) and solve for [acid].
The pKa value of acetic acid is 4.76. This value represents the acid dissociation constant of acetic acid, which is a measure of how easily the acid donates a proton in solution. A lower pKa value indicates a stronger acid, while a higher pKa value indicates a weaker acid.
No, the Henderson Hasselback equation is specifically designed for weak acids and their conjugate bases. Strong acids, which completely dissociate in solution, do not have a conjugate base and therefore cannot be used with this equation.