How many grams of nitrogen dioxide contain 1.25 x 10^22 oxygen atoms

I know that it is NO2 and that NO2 mass is 46.01g and that 1 mol of anything is 6.022 x 10^23 but I can't seem to figure out the formula

a) 0.478g
b) 0.955g
c) 0.554g
d) 0.222g

The correct answer is A but can someone please explain how to get there?

Determine the moles of oxygen by dividing by Avogadro's number

n(O) = 1.25x10^22 atoms / 6.02x10^23 atoms/mol = 0.02076 mol

There are two moles of oxygen in one mole of nitrogen dioxide, so the moles of NO2 is half the moles of O; 1:2 mole ratio.

n(NO2) = 0.02076 / 2 = 0.01038 mol

Determine the mass of NO2 by multiply the moles by the molar mass

mass = (0.01038 mol)(46.01 g/mol) = 0.478 g

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Becky, if it wasn't obvious enough, the correct answer is given.

Remember that one mole of any substance is equal to Avagadro's number or 6.022 x 10^23 atoms, molecules, etc.

Nitrogen Dioxide has a molecular weight of: 46.0055 g/mol

1.25 x 10^22/6.022 x 10^23 = 1.25/6.02 x 10^(22 - 23) = 0.20757 x 10^-1 Mole = 2.0757 x 10^-2 Mole

2.076 x 10^-2 Mole x 46.055 g/mole = 2.076 x 10^-2 Mole x 4.6055 x 10^1 g/mole = 0.9561 grams.

So it is b that is the answer, plus or minus a slight error in calculator...