Is the answer pH = 8.34, if so I need help with the explaining.

Question

What is the pH of a 0.350 M solution of lithium citrate? (Ka Citric Acid = 7.4 x 10-4)

Answer 1

No, the answer is not 8.34. This is a weak acid, so the pH would likely be below 7, not above 7. How did you come up with 8.34?

pH = -log [H⁺], so we need to find [H⁺]

Let citric acid = HA

HA <==> H⁺ + A^-

Ka = 7.4x10^-4 = [H⁺][A^-]/[HA]

7.4x10^-4 = (x)(x) / 0.350 - x

2.59x10^-4 - 7.4x10^-4x = x²

x² + 7.4x10^-4x - 2.59x10^-4 = 0

x = 0.0157 = [H⁺]

pH = -log 0.0157

pH = 1.80