Here's how to calculate the moles of aluminum hydroxide (Al(OH)₃) in 39.0 g:

1. Find the molar mass of Al(OH)₃:

* Aluminum (Al): 26.98 g/mol

* Oxygen (O): 16.00 g/mol (x 3 = 48.00 g/mol)

* Hydrogen (H): 1.01 g/mol (x 3 = 3.03 g/mol)

Total molar mass = 26.98 + 48.00 + 3.03 = 78.01 g/mol

2. Use the formula: moles = mass / molar mass

* moles = 39.0 g / 78.01 g/mol

* moles ≈ 0.500 mol

Therefore, 39.0 g of aluminum hydroxide is approximately equal to 0.500 moles.