1. Calculate the molar mass of aluminum oxide (Al₂O₃):

* Al: 26.98 g/mol (atomic weight) * 2 = 53.96 g/mol

* O: 16.00 g/mol * 3 = 48.00 g/mol

* Total molar mass: 53.96 g/mol + 48.00 g/mol = 101.96 g/mol

2. Convert grams of aluminum oxide to moles:

* Moles = (grams of solute) / (molar mass of solute)

* Moles = 51 g / 101.96 g/mol = 0.500 moles

3. Convert milliliters of solution to liters:

* Liters = (milliliters) / 1000

* Liters = 500 mL / 1000 = 0.500 L

4. Calculate the molarity:

* Molarity (M) = (moles of solute) / (liters of solution)

* Molarity = 0.500 moles / 0.500 L = 1.00 M

Therefore, the molarity of the solution is 1.00 M.