Determine the amount of substance in aluminum oxide weighing 175 g.

The amount of a substance is the number of moles of aluminum oxide in a given mass of this substance. In order to carry out the calculations, we turn to the Periodic Table of D.I. Mendeleev, and calculate the molar mass of aluminum oxide:
M (Al2O3) = 2 * 26 + 3 * 16 = 52 + 48 = 100 g / mol
Now we calculate the amount of oxide substance, for which we divide the mass by the molar mass of the oxide:
n (Al2O3) = m (Al2O3) / М (Al2O3) = 175/100 = 1.75 mol.
Answer: 1.75 mol