Final answer:
The nitrate ion concentration in a 0.900 M Al(NO₃)₃ solution is 2.7 M since each mole of Aluminum nitrate dissociates into three moles of nitrate ions.
Step-by-step explanation:
The concentration of nitrate ions (NO³⁻) in a given solution of Aluminum nitrate, Al(NO₃)₃, is contingent on the dissociation of the compound in water. For every mole of Al(NO₃)₃ that dissolves, it produces one Al³⁺ ion and three NO³⁻ ions. Therefore, if we have a 0.900 M solution of Al(NO₃)₃, the concentration of Al³⁺ will also be 0.900 M, while the concentration of NO³⁻ will be three times that amount because each formula unit produces three nitrate ions.
Thus, the nitrate ion concentration in a 0.900 M Al(NO₃)₃ solution is 2.7 M (0.900 M x 3 = 2.7 M).