Mistake In Princeton's SAT Chemistry?

Test Preparation SAT Subject Test Preparation
1

<p>The ionic solid Fe(OH)3 is added to water and dissociates into tis component ions. (Fe(OH)3 ---> Fe 3+ + 3OH -) The solubility product expression is</p>

<p>C) Ksp = [Fe3+][3OH-]^3
D) Ksp = [Fe3+][OH-]^3</p>

<p>The PR book says that it is D. However, after living through AP Chem for an entire year, I am 99% sure that the answer should be C. Any comments?</p>

2

<p>It’s D. You’d write 3x in an ICE table for [OH-], but that’s because you’re relating it to [Fe3+], for which you’d put x. In other words, the concentration of the hydroxide ion is three times the concentration of the iron ion, not three times <a href=“itself”>OH-</a>.</p>

3

<p>After having payed attention in AP Chem, I am 99.9% sure the answer is D.</p>