Answer:
Cr(OH)3
Explanation:
The addition of 6M sodium hydroxide to a solution that contains chromium(III) ion leads to the net ionic reaction;
3 OH^-(aq) + Cr^3+(aq) -------> Cr(OH)3(s)
Cr(OH)3 is insoluble except an excess of the hydroxide is added then the precipitate dissolves as follows;
Cr^3+(aq) + 4OH^-(aq)------> [Cr(OH)4]^-