Question: how many oxygen atoms are present in a tablet weighing 360 mg of aspirin?
Answer: moles = 360 × 10-³ ÷180 = 2 × 10-³ mole. number of molecules in one mole = 6.023 × 10^23 ( Na) therefore, number of molecules in 2 × 10^-3 × Na. 1 molecule of aspirin contains 4 atoms of oxygen.