Asugar crystal contains approximately 2.2×1017 sucrose (c12h22o11) molecules. part a what is its mass in mg?

From the periodic table:
mass of carbon = 12 grams
mass of hydrogen = 1 grams
mass of oxygen = 16 grams
molar mass of surcose = 12(12) + 22(1) + 11(16) = 342 grams

number of molecules = number of moles x Avogadro's number
number of moles = number of molecules / Avogadro's number
number of moles = (2.2x10^17) / (6.02x10^23) = 3.6544 x 10^-7 moles

number of moles = mass / molar mass
mass = number of moles x molar mass
mass = 3.6544 x 10^-7 x 342 = 1.249 x 10^-4 grams = 0.12498 mg