Question

aluminum nitrate dihydrate express your answer as a chemical formula.

Explanation:

Step1: Identify ions and hydrate

Aluminum ion: $Al^{3+}$, nitrate ion: $NO_3^-$, dihydrate means 2 $H_2O$.

Step2: Balance charges for aluminum nitrate

Aluminum has +3, nitrate has -1. So formula for aluminum nitrate: $Al(NO_3)_3$.

Step3: Add dihydrate

Append $\cdot 2H_2O$ to the formula.

Answer:

$\ce{Al(NO_{3})_{3}\cdot 2H_{2}O}$