As a chemist for an agricultural products company, you have just developed a new

Question

As a chemist for an agricultural products company, you have just developed a new herbicide,"Herbigon," that you think has the potential to kill weeds effectively. A sparingly soluble salt, Herbigon is dissolved in 1 M acetic acid for technical reasons having to do with its production. You have determined that the solubility product Ksp of Herbigon is 8.90×106. Although the formula of this new chemical is a trade secret, it can be revealed that the formula for Herbigon is X-acetate (XCH3COO, where "X" represents the top-secret cation of the salt). It is this cation that kills weeds. Since it is critical to have Herbigon dissolved (it won't kill weeds as a suspension), you are working on adjusting the pH so Herbigon will be soluble at the concentration needed to kill weeds. What pH must the solution have to yield a solution in which the concentration of X+ is 4.00×103 M ? The pKa of acetic acid is 4.76.

Explanation / Answer

Solution:

X (Herbigon) + CH3COOH <----> X-CH3COO- + H2O

given pKa = 4.76 Ksp=8.90*10-6 = [X][Acetic acid] =[X][1]

[X] = 8.90*10-6

by hendersen-hasselbalch equation,

pH = pKa - log{[conj.base]/[conj.acid]}     

      = 4.76 -log {[4.00*10-3] / [1]}

      = 4.76 - (-2.3979)

      = 7.1579

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.