Part B As a chemist for an agricultural products company, you have just develope
ID: 1018215 • Letter: P
Question
Part B 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 9.10×106. 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 1.50×103 M ? The pKa of acetic acid is 4.76. Express your answer numerically.
Explanation / Answer
if X+ = 1.50×103 M then CH3COO- is also 1.5 x 10^-3 M
XCH3COO is the salt of weak acid and strong base so pH should be more than 7. for this type of salts
pH = 7 + 1/2 [pKa + log C]
pH = 7 + 1/2 [4.76 + log 1.50 x 10^-3]
pH = 7.97