Farmers who raise cotton once used arsenic acid,H₃AsO₄,as a defoliant at harvest time.Arsenic acid is a polyprotic acid with K_a1 = 2.5 × 10^-⁴,K_a2 = 5.6 × 10^-⁸,and K_a3 = 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 is primarily determined by the first dissociation constant (Ka1) because it is much larger than Ka2 and Ka3. Using the formula for pH = -log[H+], where [H+] is approximately equal to the square root of (Ka1 × concentration), we find pH ≈ 1.95.

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

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