Menthol, the substance we can smell in mentholated cough drops, is composed of c, h, and o. a 6.030×10−2 −mg sample of menthol is combusted, producing 0.1697 mg of co2 and 6.954×10−2 mg of h2o. what is the empirical formula for menthol?

The empirical formula is =

Explanation:

Mass of water obtained =

Also, 1 mg = g

So, mass of water =

Molar mass of water = 18 g/mol

Moles of = /18 g/mol =  3.8634×10⁻⁶ moles

2 moles of hydrogen atoms are present in 1 mole of water. So,

Moles of H = 2 x 3.8634×10⁻⁶ = 7.7267×10⁻⁶ moles

Molar mass of H atom = 1.008 g/mol

Mass of H in molecule = 7.7267×10⁻⁶ x 1.008 = 7.6653×10⁻⁶ g

Mass of carbon dioxide obtained = 0.1697 mg

Also, 1 mg = g

So, mass of carbon dioxide =

Molar mass of carbon dioxide = 44.01 g/mol

Moles of =  /44.01 g/mol = 3.856×10⁻⁶ moles

1 mole of carbon atoms are present in 1 mole of carbon dioxide. So,

Moles of C = 3.856×10⁻⁶ moles

Molar mass of C atom = 12.0107 g/mol

Mass of C in molecule = 3.856×10⁻⁶ x 12.0107 = 46.3132 ×10⁻⁶ g

Given that the Menthol only contains hydrogen, oxygen and carbon. So,

Mass of O in the sample = Total mass - Mass of C  - Mass of H

Mass of the sample =

Also, 1 mg = g

So, mass of sample =

Mass of O in sample = ( 60.30 - 7.6653 - 46.3132 ) ×10⁻⁶ g= 6.3215×10⁻⁶ g

Molar mass of O = 15.999 g/mol

Moles of O  = 6.3215×10⁻⁶  / 15.999  = 0.3951×10⁻⁶ moles

Taking the simplest ratio for H, O and C as:

7.7267×10⁻⁶ : 0.3951×10⁻⁶ : 3.856×10⁻⁶

= 20 : 1 : 10

The empirical formula is =

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.