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?
Alex/Brandon/Dean/Matthew -- please use the same name for your posts.
To find the empirical formula of the compound, we need to determine the number of moles of carbon, hydrogen, and oxygen in the compound.
1. Determine the number of moles of carbon dioxide (CO2):
- The molar mass of CO2 is 44.01 g/mol (12.01 g/mol for carbon and 16.00 g/mol for oxygen).
- The mass of CO2 produced is 1.014 g.
- Convert the mass of CO2 to moles by dividing by the molar mass:
moles of CO2 = 1.014 g / 44.01 g/mol
= 0.0231 mol CO2
2. Determine the number of moles of water (H2O):
- The molar mass of H2O is 18.02 g/mol (2.02 g/mol for hydrogen and 16.00 g/mol for oxygen).
- The mass of H2O produced is 0.498 g.
- Convert the mass of H2O to moles by dividing by the molar mass:
moles of H2O = 0.498 g / 18.02 g/mol
= 0.0276 mol H2O
3. Determine the number of moles of carbon and hydrogen in the compound:
- The combustion of the compound indicates that all the carbon in the compound is converted to CO2 and all the hydrogen is converted to H2O.
- From the ratio of moles of C to moles of CO2, we can determine the number of moles of carbon:
moles of C = moles of CO2 = 0.0231 mol CO2
- From the ratio of moles of H to moles of H2O, we can determine the number of moles of hydrogen:
moles of H = 2 * moles of H2O = 2 * 0.0276 mol H2O
= 0.0552 mol H
4. Calculate the empirical formula:
- The empirical formula shows the simplest whole number ratio of atoms in a compound.
- Divide the number of moles of each element by the smallest number of moles to get the simplest whole number ratio.
Empirical formula of the compound = C0.0231H0.0552 (rounded to the nearest whole number)
= CH2
Therefore, the empirical formula of the compound is CH2.
To determine the empirical formula of the organic compound, we need to calculate the ratio of the elements present in the compound. In this case, we are given the mass of carbon dioxide (CO2) and water (H2O) produced during combustion analysis.
Step 1: Calculate the moles of CO2 produced:
1. Calculate the molar mass of CO2:
Molar mass of C = 12.01 g/mol
Molar mass of O = 16.00 g/mol
Molar mass of CO2 = (12.01 g/mol × 1) + (16.00 g/mol × 2) = 44.01 g/mol
2. Calculate the number of moles of CO2:
Moles of CO2 = mass of CO2 / molar mass of CO2
= 1.014 g / 44.01 g/mol
Step 2: Calculate the moles of H2O produced:
1. Calculate the molar mass of H2O:
Molar mass of H = 1.01 g/mol
Molar mass of O = 16.00 g/mol
Molar mass of H2O = (1.01 g/mol × 2) + (16.00 g/mol × 1) = 18.02 g/mol
2. Calculate the number of moles of H2O:
Moles of H2O = mass of H2O / molar mass of H2O
= 0.498 g / 18.02 g/mol
Step 3: Determine the empirical formula:
1. Find the ratio of carbon to hydrogen:
Divide the moles of C by the smallest number of moles obtained. In this case, we’ll use H2O as the reference.
Carbon ratio = moles of CO2 / moles of H2O
2. Find the ratio of hydrogen to oxygen:
Divide the moles of H2O by the smallest number of moles obtained. Again, we'll use H2O as the reference.
Hydrogen ratio = moles of H2O / moles of H2O (which is essentially 1 since moles of H2O = moles of H2O)
3. Compare the ratios obtained:
Multiply both ratios by a factor to ensure both numbers are whole numbers. This factor should be the smallest whole number that will convert one of the ratios into a whole number.
4. Write the empirical formula:
The empirical formula is written with the element symbol and the ratio of the atoms.
Now, using the values you calculated, you can determine the empirical formula of the compound.