A lab manual states that to prepare a certain buffer requires mixing 25 ml of 0.200 M HClO (Ka=3.00 x 10^-8) with 50 ml of 0.2 M NaClO What is the Ph of this buffer?
To find the pH of the buffer, we need to calculate the concentration of the acid and its conjugate base after mixing. Then we can use the Henderson-Hasselbalch equation, which relates the pH of a buffer solution to the concentration of the acid and base.
First, let's calculate the concentration of HClO after mixing the 25 ml of 0.200 M HClO with 50 ml of water.
concentration of HClO = (volume of HClO / total volume) * initial concentration
= (25 ml / (25 ml + 50 ml)) * 0.200 M
≈ 0.067 M
Next, let's calculate the concentration of the conjugate base, ClO-, using the concentration of NaClO.
concentration of ClO- = (volume of NaClO / total volume) * initial concentration
= (50 ml / (25 ml + 50 ml)) * 0.200 M
≈ 0.133 M
Now, we can use the Henderson-Hasselbalch equation:
pH = pKa + log10(concentration of A- / concentration of HA)
The pKa value is given as 3.00 x 10^-8. Let's substitute the values:
pH = -log10(3.00 x 10^-8) + log10(0.133 M / 0.067 M)
≈ 7.90
Therefore, the pH of this buffer is approximately 7.90.