A buffer is prepared containing 0.300 molar boric acid and 0.500 molar dihydrogen borate. What is its pH? (pKa = 9. 27)

To solve this problem, we can use the Henderson-Hasselbalch equation, which is used to estimate the pH of a buffer solution. The equation is as follows:

pH = pKa + log([A-]/[HA])

where:

• pH is the pH of the buffer,
• pKa is the acid dissociation constant,
• [A-] is the concentration of the base (in this case, dihydrogen borate),
• [HA] is the concentration of the acid (in this case, boric acid).

Given in the problem, we have:

• pKa = 9.27,
• [A-] = 0.500 M (concentration of dihydrogen borate),
• [HA] = 0.300 M (concentration of boric acid).

Substituting these values into the Henderson-Hasselbalch equation, we get:

pH = 9.27 + log(0.500/0.300)

To simplify this, we first calculate the value of the log term:

log(0.500/0.300) = log(1.67) ≈ 0.22

Then we substitute this back into the equation:

pH = 9.27 + 0.22 = 9.49

So, the pH of the buffer solution is approximately 9.49.