Combustion analysis of toulene, a common organic solvent gives 5.86 mg of CO2 and 1.37 mg of H20.?

Question

Find the empirical formula. Can someone please explain how to do this, in a couple of steps.

Answer 1

molecular mass of
H:1
C:12
H2O:18
CO2: 44

5.86 mg of CO2 contains 5.86*12/44 mg C = 1.60 mg C
1.60 mg C corresponds to 1.60/12 mmol C = 0.133 mmol C

1.37 mg of H20 contains 1.37*1*2/18 mg H = 0.152 mg H
0.152 mg H corresponds to 0.152 mmol H

The molar ratio C/H is 0.133/0.152 is 1/1.14

1/1.14 or
2/2.28
3/3.52
.
7/8 <- bingo! ... so the formula is C7H8

Answer 2

Use the molecular weights of CO2 and H2O to determine the number of moles of carbon and hydrogen (toluene only has C and H in it). Divide the number of moles of each by the smallest number you have. Multiply so that you have whole numbers (1, 2, 3...) for both C and H.

Answer 3

To find the Empirical Formula, you need the simplest ratios of the moles of each element in a compound. Because the products contain elements of C, H and O, you know that toluene is made up of only these elements. So you simply need to find the moles of C, H and O produced and put them in their simplest ratio.
To find the moles of C, determine the mass of C produced by dividing the atomic mass of C by the total molar mass of CO2. Once you've found this mass, you can evaluate the number of moles by dividing by the molar mass of C.
To find the moles of H, determine the mass of H prduced by dividing 2 times the atomic mass of H by the total atomic mass of Water. Once you've done this, find the moles of H by dividing by the atomic mass of H.
To find the moles of O produced, you need the original mass of toluene. Find the mass of O produced by subtracting the sum of the masses of C and H from the total mass of toluene. Then find the moles of O by dividing its mass by the atomic mass of O.
Now you have the moles of all three elements. Put these numbers in their simplest ratio to determine the empirical formula.

Later note: In finding the moles of Oxygen, my explanation would be correct, but toluene is just a benzene ring with a methyl group attached, therefore it does not have any oxygen. So you can ignore the part with oxygen, however, the explanation I gave would be a general method of finding the empirical formula for a combusted compound consisting of C, H and O.

Answer 4

Toluene is C6H5CH3, structuraly. Chemical formula is C7H8. That is also the emperical formula.

Answer 5

moles CO2 = 0.00707 g/ 40 4.009 g/mol=0.000161 = moles C interior the compound Moles H2O = 0.00164 g/ 18.02 g/mol=0.0000910 moles H interior the compound = 0.0000910 x 2=0.000182 divide by skill of the smallest decision 0.000161 / 0.000161 = one million => C 0.000182 / 0.000161 =one million.13 => H to get entire numbers multiply by skill of seven C7H8