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
This substance is certainly not gas since gas particles have large spaces between them. This substance is certainly not solid as well since solid particles are closely packed together with very close proximity. This substance is therefore liquid since particles are still close but can move around in a disordered arrangement.
Mg=1
O=2
H=2
The 2 only affects what is in the parentheses