You considered the equilibrium: Fe3+(aq) + SCN-(aq) Fe(SCN)2+(aq), and compared the color of the solutions in four test tubes. In the third test tube, you added 6 M NaOH dropwise. How do you explain the formation of a precipitate and the shift in equilibrium in terms of LeChatelier's Principle? a. The addition of NaOH produced the precipitate, Fe(OH)3, which removed Fe3+ from the system. To reduce the stress of the removal of Fe3+ and to re-establish equilibrium, the system shifted to the left increasing [Fe3+] and decreasing the [Fe(SCN)2+]. Increasing the [Fe3+] produced a yellow colored solution. b. The addition of NaOH produced the precipitate, NaSCN, which removed SCN- from the system. To reduce the stress of the removal of SCN- and to re-establish equilibrium, the system shifted to the left increasing [SCN-] and decreasing the [Fe(SCN)2+]. Increasing the [SCN-] produced a yellow colored solution. c. The addition of NaOH produced the precipitate, Fe(SCN)(OH)2, which removed Fe(SCN)2+ from the system. The removal of Fe(SCN)2+ from the system caused the deep red color to disappear leaving only the yellow color.