Calculate the pH of the following 0.0500 M H3AsO4 and 0.0500 M NaH2AsO4?
Use the Henderson-Hasselbalch equation.
To calculate the pH of a solution, we need to consider the dissociation of the acid and its conjugate base. In this case, H3AsO4 is a weak acid and NaH2AsO4 is its conjugate base. We can use the Henderson-Hasselbalch equation to calculate the pH of the solution.
The Henderson-Hasselbalch equation is given by:
pH = pKa + log([A-]/[HA])
Where:
pH is the pH of the solution
pKa is the dissociation constant of the acid (H3AsO4)
[A-] is the concentration of the conjugate base (NaH2AsO4)
[HA] is the concentration of the acid (H3AsO4)
First, we need to determine the pKa value for H3AsO4. Looking up the pKa value for H3AsO4, we find that it is approximately 2.24.
Next, we need to determine the concentrations of the acid (H3AsO4) and its conjugate base (NaH2AsO4) in the solution. From the given information, we know that the concentrations of both H3AsO4 and NaH2AsO4 are 0.0500 M.
Now, we can substitute the values into the Henderson-Hasselbalch equation to calculate the pH:
pH = 2.24 + log([NaH2AsO4]/[H3AsO4])
= 2.24 + log(0.0500/0.0500)
= 2.24 + log(1)
= 2.24 + 0
= 2.24
Therefore, the pH of the solution containing 0.0500 M H3AsO4 and 0.0500 M NaH2AsO4 is approximately 2.24.