How can Cr(OH)4^- be an (aq) ion if it is insoluble?

Question

I"m trying to balance this one redox equation, but I cannot understand how the above ionic compound could be soluble in view of the 10th solubility rule.

Ya'll should start charging for your answers!! You would make some money off me!!

Thanks again everyone. You have been quite kind and thorough with your responses. I appreciate your patience with a chemistry neophyte.

Answer 1

Cr(OH)3 the molecule is quite insoluble,

but [CrOH)4]-1 is a very soluble complex ion

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too much of a good thing, & its dissolves

like adding  Cl- to Ag+ , first you see the ppt, then you add too much & it starts to dissolve as [Ag(Cl-)2]-