How many moles are represented by each of these samples?

Question

(a) 180.0 g Fe2O3:

(b) 16.0 mg NO2:

sig figs are needed so please included them

Answer 1

morga is on the right track, but has the wrong molar mass for Fe2O3...  her's is the molar mass of FeO3

180.0 g Fe2O3 @  159.69 g/mol = 1.12718 moles

your answer (4 sig figs) : 1.127 moles

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16.0 mg NO2 @ 46.0055 mg/mmol = 0.34778 mmoles

0.34778 mmoles = 3.48 e -4 moles

your answer ( 3 sig figs ) : 3.48e-4 moles NO2

& you meant 16.0 milligrams ,

Answer 2

180.0g Fe2O3 * 1mol Fe2O3/103.845g = 1.733 moles Fe2O3

16.0mg NO2 * 1 gram/1000mg * 1 mol NO2/46.005g NO2 = .000348 moles NO2