Question

Menthol, from the oil of mint, has a characteristically cool taste. The compound contains only C, H, and O. If 95.6 mg of menthol burns completely in O₂ and gives 269 mg of CO₂ and 110 mg of H₂O, what is the empirical formula of menthol? Please answer here: What is the number of moles of H that were present in this menthol sample?

a) 0.00625 moles
b) 0.0125 moles
c) 0.01875 moles
d) 0.025 moles

Answer 1

To find the number of moles of hydrogen, the mass of H produced in water during combustion is used. Calculating from the mass of H₂O given, the number of moles of H from the menthol sample is closest to 0.0125 moles, making option (b) the correct answer.

Step-by-step explanation:

To determine the number of moles of H present in the menthol sample, we first find the mass of hydrogen by using the mass of water produced. For every 1 mole of H₂O, there are 2 moles of H atoms, which means that 18 g of H₂O contains 2 g of H. We calculate the moles of H from the mass of H₂O produced by:

Mass of H in H₂O = (110 mg / 18 g/mol H₂O) × (2 g/mol H)

Since 1 g = 1000 mg, we convert 110 mg to grams:
110 mg = 0.110 g

Therefore:
Mass of H = (0.110 g / 18 g/mol) × (2 g/mol)
Mass of H = 0.0122 g of H

Finally, convert the mass of H to moles:
Moles of H = 0.0122 g / (1 g/mol)
Moles of H = 0.0122 moles

Since 0.0122 moles is closest to the option (b) 0.0125 moles, that is our answer.