As a chemist for an agricultural products company, you have just developed a new
ID: 607984 • Letter: A
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 1M acetic acid for technical reasons having to do with its production. You have determined that the solubility product Ksp of Herbigon is 8.80Explanation / Answer
The question is assuming that when acid is added to XAc (Ac = acetate ion), it reacts with the Ac forming X and HAc b/c H has a strong attraction for Ac which gives it the ability to force XAc to dissolve. The equation for disassociation of all the ions involved is: ......................XAc(s) + HAc(aq) ~> X(aq) + H(aq) + Ac(aq) initial conc......................1M ............. 0............ 0.......... 0 change.............................. -a............ 0.006........ a..... a+0.006 final................................. 1-a ............ 0.006....... a...... a+0.006 The acid-base equilibrium relation for acetic acid is used to find H and pH: Ka = [H][Ac]/[HAc] = a(a+0.006)/(1-a) = 10^(-4.76) = 1.74x10^-5. The 10^(-4.76) is the Ka obtained from pKa. Simplify the equation: a^2+0.0060174a-1.74x10^-5=0 Solve: a=0.00213M=[H] pH=-log[H]=2.22
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