An organic compound containing only C, H, and possibly O was subjected to combustion analysis. A
sample weighing 0.4801 g yielded 1.014 g CO2 and 0.498 g H2O. What is the empirical formula of the compound?
I got C5H12O2. Please let me know if this is correct.
yes. Go to the front of the class.Very good.
So... its correct?
Yes.
To determine the empirical formula of the organic compound, we need to calculate the ratio of the elements present in the compound based on the masses of the combustion products.
We have the following information:
Mass of CO2 produced = 1.014 g
Mass of H2O produced = 0.498 g
Total mass of the sample = 0.4801 g
1. First, we need to convert the masses of CO2 and H2O produced into moles. We can use the molar masses to do this.
Molar mass of CO2 = 12.01 g/mol + 2 * 16.00 g/mol = 44.01 g/mol
Molar mass of H2O = 2 * 1.01 g/mol + 16.00 g/mol = 18.02 g/mol
Moles of CO2 = mass of CO2 / molar mass of CO2 = 1.014 g / 44.01 g/mol ≈ 0.0230 mol
Moles of H2O = mass of H2O / molar mass of H2O = 0.498 g / 18.02 g/mol ≈ 0.0276 mol
2. Next, we need to determine the number of moles of carbon (C), hydrogen (H), and oxygen (O) in the compound.
In CO2, there is 1 mole of carbon (C) and 2 moles of oxygen (O).
In H2O, there are 2 moles of hydrogen (H) and 1 mole of oxygen (O).
Since the total moles of carbon in CO2 come from the organic compound, the number of moles of carbon in the organic compound is also approximately 0.0230 mol.
The total moles of hydrogen in H2O come from the organic compound, so the number of moles of hydrogen in the organic compound is approximately 2 * 0.0276 mol = 0.0552 mol.
To determine the number of moles of oxygen in the organic compound, subtract the sum of the moles of carbon and hydrogen from the total moles of the sample:
Total moles of the sample = 0.4801 g / molar mass of the sample
Assuming the sample contains only carbon, hydrogen, and oxygen, its molar mass can be calculated as:
molar mass of sample = (12.01 g/mol * number of carbon atoms) + (1.01 g/mol * number of hydrogen atoms) + (16.00 g/mol * number of oxygen atoms)
Rearranging the equation above, we can solve for the number of oxygen atoms:
number of oxygen atoms = (molar mass of sample - (12.01 g/mol * number of carbon atoms) - (1.01 g/mol * number of hydrogen atoms)) / 16.00 g/mol
Substituting the known values into the equation, we have:
number of oxygen atoms = (molar mass of sample - 12.01 g/mol * 0.0230 mol - 1.01 g/mol * 0.0552 mol) / 16.00 g/mol
3. Calculate the empirical formula.
To find the simplest whole number ratio of the atoms in the compound, divide the number of moles of each element by the smallest number of moles.
Number of moles of carbon = 0.0230 mol / 0.0230 mol = 1 mol
Number of moles of hydrogen = 0.0552 mol / 0.0230 mol ≈ 2.40 mol
Number of moles of oxygen = (molar mass of sample - 12.01 g/mol * 0.0230 mol - 1.01 g/mol * 0.0552 mol) / 16.00 g/mol / 0.0230 mol ≈ 0.274 mol
Since we need to express the empirical formula using whole numbers, we need to multiply the number of moles of each element by a common factor to obtain whole number values. In this case, the factor that gives us the simplest whole numbers is approximately 10.
Multiplying the number of moles of each element by 10:
Number of moles of carbon = 1 mol * 10 = 10
Number of moles of hydrogen = 2.40 mol * 10 = 24
Number of moles of oxygen = 0.274 mol * 10 = 2.74
Therefore, the empirical formula of the compound is C10H24O2.
So, your initial answer of C5H12O2 is not correct.