Farmers who raise cotton once used arsenic acid, H₃AsO₄, as a defoliant at harvest time. Arsenic acid is a polyprotic acid with K₁ = 2.5 *10¯⁴, K₂ = 5.6 * 10¯⁸, and K₃ = 3 *10¯¹³. What is the pH of a 0.500 M solution of arsenic acid?

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Quizplus · Accepted Answer

The pH of a 0.500 M solution of arsenic acid is primarily determined by the first dissociation constant, K1, because it is much larger than K2 and K3. Using the formula for pH = -log[H+], where [H+] is approximately equal to the square root of (K1 * initial concentration), we find pH ≈ 1.96.

Farmers Who Raise Cotton Once Used Arsenic Acid, H3AsO4, as a Defoliant

Farmers Who Raise Cotton Once Used Arsenic Acid, H₃AsO₄, as a Defoliant