Compare the moles of C, moles of H and moles of O and determine which value is t

Question

Compare the moles of C, moles of H and moles of O and determine which value is the smallest. Now take the moles of each atom (C, H, and O) and divide each by the smallest value. The whole number that you get for each atom will give you the empirical formula for catechol.

From the change in the P203 and the NaOH trap masses, determine the masses of H2O and CO2 produced. Be careful to use the change in mass of each trap for just before, and just after, the unknown sample is combusted.

Mass of H2O - ? g

Mass of CO2 - ? g

Convert the above masses into the number of moles of H2O and CO2 produced from the unknown sample.

Moles of H20 - ? moles

Moles of CO2 - ? moles

From the number of moles of H20 and CO2 produced, determine the number of moles of H atoms an C atoms in the sample.

Moles of H atoms - ? moles

Moles of C atoms - ? moles

From the above and the atomic masses of the elements, determine the masses of H and C in the sample.

Mass of H - ? g

Mass of C - ? g

Explanation / Answer

/molecular formula of Catechol is C6H6O2

Moles of C-atoms=6

Moles of H-atoms=6

Moles of O-atoms=2

smallest number=2

Dividing by this smallest value,

Mole ratio of C-atoms=6/2=3

Mole ratio of H-atoms=6/2=3

Mole ratio of O-atoms=2/2=1

The emperical formula of catechol=(C3H3O)n

An emperical formula of any compound shows the simplest ratio of atoms present in it.

Given ,

CO2 mass =13.936g

mass of H2O=7.437g

Number of moles of H2O and CO2 produced from the unknown sample.

Moles of H2O=mass of H2O/molar mass of H2O=13.936 g/18.000g/mol=0.774 moles

Moles of CO2 =mass of CO2/molar mass of CO2=7.437g/44.010 g/mol=0.169 moles

the number of moles of H atoms an C atoms in the sample.

To determine Moles of H atoms,

Each mole of H2O has 2 mole atoms of H

moles of H-atom=2*moles of H2O=2*0.774 moles=1.548 moles

To determine Moles of C atoms,

Each mole of CO2 has 1 mole atoms of C

moles of C-atom=1*moles of H2O=0.169 moles

the masses of H and C in the sample.

Mass of H = no of moles of H-atoms* atomic mass of H=1.548 moles* 1g/mol=1.548 g

Mass of C =no of moles of C-atoms* atomic mass of C=0.169 moles*12.0g/mol=2.028 g

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