The formula units of Cr(ClO2)3 that are in 6.85 moles of Cr(Clo203 is 4.1237 x10^24 formula units
calculation
the formula units are calculated using of Avogadro's law constant
that is according to Avogadro's law 1 mole = 6.02 x10 ^23 formula units
6.85 moles= ? formula units
by cross multiplication.
= ( 6.85 moles x 6.02 x10^23 formula units ) / 1 mole = 4.1237 x 10 ^24 formula units
The moles of Oxygen contained in 6.85 moles of cr(ClO2)3 is 41.1 moles
calculation
moles of oxygen = number of oxygen atom in Cr(ClO2)3 x 6.85(moles of Cr(ClO2)3
calculate the number of oxygen atoms that are in Cr(ClO2)3
that is 2 x 3 = 6 atoms of Oxygen.
moles is therefore = 6 x 6.85 moles= 41.1 moles