How many moles of Cr are in 2.16 mol of Cr2O3?

When 1 mol of Cr2O3 has 2 mol of Cr, So we can easily get the number of moles of Cr in 2.16 mol of CrO3 by:

Cr → Cr2O3

2 mol→ 1 Mol

X → 2.16 Mol

So X (the no. of mol of Cr) = 2 Mol * 2.16 Mol = 4.32 Mol