Respuesta :

molar mass of aluminum = 26.982 g/mol.
1 mol of Al = 26.9≈27g = 6.02×10²³ atoms [ avogadro's number]
meaning
1 g | Al = 6.02/27 × 10²³ atoms
so 3.78g | Al = 6.02×3.78]/27 ×10²³
= 0.8428 ×10²³ atoms
= 8.428 ×10²² atoms