Which of the following compounds would result in the reaction being more active in the reverse direction? $\ce{Fe(OH)2 (s) &lt;=&gt; Fe^{2+} + 2OH-}$
The reaction will be more active in the reverse direction if .......... is added
a) $\ce{KOH}$
b) $\ce{Na2S}$
c) $\ce{Fe(OH)2}$
d) $\ce{Fe(NO3)2}$

My thoughts:
Well, adding more $\ce{KOH}$ will increase the $\ce{OH-}$ ions so the reaction will go in the reverse direction to get back to equilibrium. Adding $\ce{Fe(NO3)2}$ Will increase $\ce{Fe^{2+}}$ ions and the reaction will go in the reverse direction too.
However, the book answers states that only (d) $\ce{Fe(NO3)2}$. I searched google but all the examples involved having only choice which works.
Note: Refer me to sites if necessary. I am ready to read.
In fact, adding more ion hydroxide won't displace the equilibrium towards the reverse reaction. This is due to the fact that ion complex $\ce{[Fe(OH)4]^{-2}}$, which is stable in presence of excess of ion hydroxide, is formed by successive addition of ion hydroxide on ferrous hydroxide.
If you want to study this more in depth, I invite you to read this webpage
It's explained at the end of the page under &quot;numerical problems&quot;.