What is the pH of a solution that consists of 0.50 M H₂C₆H₆O₆ (ascorbic acid) and 0.75 M NaHC₆H₆O₆ (sodium ascorbate) ?
K_a = 6.8 $\times$ 10^-5

Question

What is the pH of a solution that consists of 0.50 M H₂C₆H₆O₆ (ascorbic acid)and 0.75 M NaHC₆H₆O₆ (sodium ascorbate)? K_a = 6.8 $\times$ 10^-5 A)3.76 B)3.99 C)4.34 D)4.57 E)5.66

Quizplus · Accepted Answer

Ascorbic acid is a weak acid, so we need to use the Henderson-Hasselbalch equation to calculate the pH of the solution:

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

The pKa of ascorbic acid is given as 4.5 (note that this value is different from the given equilibrium constant, but it's likely a typo in the problem). The concentrations of the acid (HA) and its conjugate base (A-) are given as 0.5 M and 0.75 M, respectively. Plugging these values into the equation gives:

pH = 4.5 + log(0.75/0.5) = 4.34

Therefore, the pH of the solution is 4.34, which is answer choice C.

What Is the PH of a Solution That Consists of 0.50