What is the pH of a buffer solution that is 0.2 M in HCO3- and 2 M in H2CO3, given the first pKa of carbonic acid is 6.37?

What is the pH of a buffer solution that is 0.2 M in HCO3- and 2 M in H2CO3, given the first pKa of carbonic acid is 6.37?

• A. 4.37
• B. 5.37
• C. 6.37
• D. 7.37

Answer: (B)

To determine the pH of the buffer solution composed of bicarbonate ion (HCO3-) and carbonic acid (H2CO3), the Henderson-Hasselbalch equation is utilized. This equation is particularly useful for calculating the pH of buffer solutions and is given by the formula: \[ \text{pH} = \text{pKa} + \log\left(\frac{[\text{A}^-]}{[\text{HA}]}\right) \] In this situation, H2CO3 acts as the weak acid (HA) and HCO3- serves as its conjugate base (A⁻). From the problem, we know: - The concentration of H2CO3 is 2 M. - The concentration of HCO3- is 0.2 M. - The first pKa of carbonic acid (H2CO3) is given as 6.37. Now we can plug these values into the Henderson-Hasselbalch equation: 1. Start by substituting into the equation: \[ \text{pH} = 6.37 + \log\left(\frac{0.2}{2}\right) \] 2

To determine the pH of the buffer solution composed of bicarbonate ion (HCO3-) and carbonic acid (H2CO3), the Henderson-Hasselbalch equation is utilized. This equation is particularly useful for calculating the pH of buffer solutions and is given by the formula:

[ \text{pH} = \text{pKa} + \log\left(\frac{[\text{A}^-]}{[\text{HA}]}\right) ]

In this situation, H2CO3 acts as the weak acid (HA) and HCO3- serves as its conjugate base (A⁻). From the problem, we know:

• The concentration of H2CO3 is 2 M.

• The concentration of HCO3- is 0.2 M.

• The first pKa of carbonic acid (H2CO3) is given as 6.37.

Now we can plug these values into the Henderson-Hasselbalch equation:

1. Start by substituting into the equation:

[ \text{pH} = 6.37 + \log\left(\frac{0.2}{2}\right) ]

2