Answer:
aluminum forms a complex ion with excess hydroxide
Step-by-step explanation:
Complex formation accounts for the dissolution of certain compounds. For instance,reaction of aluminum and sodium hydroxide yields insoluble aluminum hydroxide as follows;
Al(s) + 3NaOH(aq) -----> Al(OH)3(s) +Na(s)
However, in excess NaOH, the solid aluminum hydroxide dissolves as due to the formation of a complex Al(OH)4^- in the solution.