Anthracene which contains only Carbon and hydrogen, is an important source of dyes. When 250 mg of anthracene is burned in pure oxygen, 8.64 mg of CO2 and 1.26 mg of H2O are formed. What is the empirical formula of anthracene?
The easist, I think, but a little longer is to convert to percent.
%C = 8.64 x (12/44)/250 = %C
12 is atomic mass C. 44 is molar mass CO2.
%H = 1.26 x (2*1/18)/250 = %H.
Then take a 100 g sample, convert to mols C and mols H and find the ratio. Post your work if you get stuck and I can help you throgh.
molar mass
To determine the empirical formula of anthracene, we need to find the ratio of carbon to hydrogen.
First, let's calculate the number of moles of CO2 formed. We can use the molar mass of CO2 to convert the mass of CO2 to moles.
Molar mass of CO2 = 12.01 g/mol (carbon) + 2 * 16.00 g/mol (oxygen) = 44.01 g/mol
Moles of CO2 = mass of CO2 / molar mass of CO2 = 8.64 mg / 44.01 g/mol = 0.1962 mmol
Next, let's calculate the number of moles of H2O formed. We can use the molar mass of H2O to convert the mass of H2O to moles.
Molar mass of H2O = 2 * 1.01 g/mol (hydrogen) + 16.00 g/mol (oxygen) = 18.02 g/mol
Moles of H2O = mass of H2O / molar mass of H2O = 1.26 mg / 18.02 g/mol = 0.0699 mmol
Now, let's determine the number of moles of carbon and hydrogen in the 250 mg of anthracene.
Molar mass of carbon = 12.01 g/mol
Molar mass of hydrogen = 1.01 g/mol
Moles of carbon = mass of anthracene / molar mass of carbon = 250 mg / 12.01 g/mol = 20.82 mmol
Moles of hydrogen = mass of anthracene / molar mass of hydrogen = 250 mg / 1.01 g/mol = 247.52 mmol
Finally, let's find the ratio of carbon atoms to hydrogen atoms.
Carbon: Hydrogen = Moles of carbon / Moles of hydrogen
= 20.82 mmol / 247.52 mmol
= 0.08406
From the calculation, we find that the ratio of carbon to hydrogen is approximately 0.08406.
The empirical formula of a compound represents the simplest whole number ratio of atoms in the compound. To find the empirical formula, we need to simplify the ratio. We can multiply it by a common factor to get whole numbers.
In this case, we can multiply the ratio by 12 to get a whole number.
Carbon: Hydrogen = 0.08406 * 12 ≈ 1.0087
The ratio of carbon to hydrogen is approximately 1:1.
The empirical formula of anthracene is CH.