Calculate the pH of a buffer that is 0.250M in NaHCO3 and 0.300M in Na2CO3

Use the Henderson-Hasselbalch equation.

Na2CO3 is the base; NaHCO3 is the acid.

To calculate the pH of a buffer solution, we need to use the Henderson-Hasselbalch equation. This equation is given by:

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

Where pH is the desired pH of the buffer, pKa is the negative logarithm of the acid dissociation constant of the weak acid in the buffer, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid.

In this case, NaHCO3 is a weak acid (HA) and Na2CO3 is its conjugate base (A-). The pKa value for the bicarbonate ion (HCO3-) is about 6.35. Now let's substitute the values into the equation and calculate the pH:

[A-] = 0.300 M (concentration of Na2CO3)
[HA] = 0.250 M (concentration of NaHCO3)
pKa = 6.35 (pKa value for HCO3-)

pH = 6.35 + log (0.300 / 0.250)
pH = 6.35 + log (1.2)

To find the value of log(1.2), we can use a scientific calculator or an online calculator. Plugging in the numbers, we get:

pH ≈ 6.35 + 0.079
pH ≈ 6.43

Therefore, the pH of the buffer solution is approximately 6.43.