What volumes of 0.47 M HF and 0.47 M NaF must be mixed to prepare 1.00 L of a solution buffered at pH = 3.50?
HF
NaF
To determine the volumes of 0.47 M HF and 0.47 M NaF needed to prepare a 1.00 L solution buffered at pH 3.50, we need to use the Henderson-Hasselbalch equation:
pH = pKa + log ([A-]/[HA])
Here, HA represents the weak acid (HF) and A- represents its conjugate base (F-).
First, determine pKa of HF. The pKa value for HF is 3.17.
Now, let's solve the Henderson-Hasselbalch equation for the given pH and pKa:
3.50 = 3.17 + log ([F-]/[HF])
To simplify the equation, we need the ratio of [F-]/[HF]. Since we are preparing a buffer solution, the ratio should be 1.
Therefore,
3.50 = 3.17 + log (1)
Since the log (1) is 0, we get:
3.50 = 3.17 + 0
To prepare a buffer solution at pH 3.50, the ratio of [F-]/[HF] should be 1. Thus, to prepare 1.00 L of the buffer solution, you would need an equal volume of HF and NaF.
Therefore, you would need to mix 0.50 L of 0.47 M HF and 0.50 L of 0.47 M NaF to prepare 1.00 L of the solution buffered at pH 3.50.