Menthol is composed of C, H, and O. A 0.1005g sample of menthol is combusted, producing 0.2829g of CO2 and 0.1159g H2O. What is the empirical and molecular formula for menthol?

Question

The compound has a molar mass of 156.30g/mol.

Henry Antrim · Accepted Answer

Well, let us see.....I make it #C_10H_20O#

#"Moles of carbon dioxide"=(0.2829*g)/(44.01*g*mol^-1)=6.43*mmol#...there were thus...................

#6.43xx10^-3xx12.011*g*mol^-1=0.07721*g# with respect to CARBON in the original #0.1005*g# mass.

#"Moles of water"=(0.1159*g)/(18.01*g*mol^-1)=6.43*mmol#...there were thus...................

#6.44xx10^-3xx2xx1.00794*g*mol^-1=0.01927*g# with respect to HYDROGEN in the original #0.1005*g# mass.

And so we have accounted for #90.18*mg#...the balance was oxygen...#0.01032*g-=6.45xx10^-4*mol#...

And so empirical formula....#C_((0.00643*mol)/(6.45xx10^-4*mol))H_((0.01286*mol)/(6.45xx10^-4*mol))O_((6.45xx10^-4*mol)/(6.45xx10^-4*mol))#

In this case, we have divided by the LEAST molar quantity, which is oxygen.

#-=C_10H_20O_1-=C_10H_20O#

But we know that the #"molecular formula"# is a whole number of the multiple of the #"empirical formula"#....therefore....

#156.3*g*mol^-1-=nxx(12.011xx10+1.00794xx20+16.00)*g*mol^-1#...

Clearly, #n=1#, and here the #"molecular formula"# is the same as the #"empirical formula"#. I hope you can see the formatting in this answer. I am having trouble. Menthol is truly a lovely organic chemical with a beautiful smell....and it is very commonly used as a flavouring...

Serenity Allen · Answer

undefined The empirical formula for menthol can be found by first calculating the moles of carbon, hydrogen, and oxygen from the given masses of CO2 and H2O produced during combustion. Then, find the simplest whole-number ratio of these elements to obtain the empirical formula: 1. Calculate the moles of carbon: Moles of CO2 = Mass of CO2 / Molar mass of CO2
 Moles of carbon = Moles of CO2 (since one mole of CO2 contains one mole of carbon)
2. Calculate the moles of hydrogen: Moles of H2O = Mass of H2O / Molar mass of H2O
 Moles of hydrogen = 2 × Moles of H2O (since one mole of H2O contains two moles of hydrogen)
3. Calculate the moles of oxygen: Moles of oxygen = (Moles of CO2 × 2) + Moles of H2O (since one mole of CO2 contains two moles of oxygen)
4. Find the simplest whole-number ratio of moles of menthol.