Vanillin, c8h8o3 (m = 152 g/mol), is the molecule responsible for the vanilla flavor in food. how many oxygen atoms are present in a 45.0 mg sample of vanillin?

Molecular weight of vanillin = 152 g/mol

Futher molecular formula of vanillin is C8H8O3

Atomic weight of oxygen = 16 g/mol

Thus, 152 g of vanillin contains 16 g of oxygen
∴   0.045 g  (45 mg) of vanillin contains  = 0.00473 g

Also, number of moles of vanillin in 0.045 g sample = 
Now, 1  mole = 6.023 X 10^23 molecules
∴    2.96 X 10^-4 mole = 1.78 X 10^20 molecules

From molecular formula, it can be seen that 1 molecule of vanallin contain 3 atoms of oxygen
∴1.78 X 10^20 molecules contain 3 X 1.78 X 10^20 = 5.34 X 10^20 oxygen atoms

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