The structural formula for acetic acid is CH3CO2H. What is its empirical formula; what is its molecular formula?
The empirical formula is the simplest formula, but first you need the molecular formula by colelcting the same elements together.
CH3CO2H
molecular formula is C2H4O2
simplest is then CH2O
To determine the empirical formula of acetic acid, we need to find the simplest whole number ratio of atoms in the compound.
1. Start by listing the number of each type of atom in the compound:
- Carbon (C): 2
- Hydrogen (H): 4
- Oxygen (O): 2
2. Divide each of the atom counts by their greatest common divisor (GCD) to simplify the ratio:
- GCD of C, H, and O is 2, so divide each count by 2:
- C: 2 ÷ 2 = 1
- H: 4 ÷ 2 = 2
- O: 2 ÷ 2 = 1
3. The resulting ratio is:
- C: 1
- H: 2
- O: 1
Therefore, the empirical formula of acetic acid is CH2O.
To find the molecular formula, we need to know the molar mass of acetic acid:
- Carbon (C) atomic mass: 12.01 g/mol
- Hydrogen (H) atomic mass: 1.008 g/mol
- Oxygen (O) atomic mass: 16.00 g/mol
Using these atomic masses, we can find the molar mass of the empirical formula (CH2O):
- C: 12.01 g/mol × 1 = 12.01 g/mol
- H: 1.008 g/mol × 2 = 2.016 g/mol
- O: 16.00 g/mol × 1 = 16.00 g/mol
The molar mass of the empirical formula (CH2O) is 30.026 g/mol.
The molecular formula represents the actual number of atoms present in a molecule. To find the molecular formula, we need to divide the molar mass of the compound by the molar mass of the empirical formula:
- Molecular formula = Molar mass of acetic acid / Molar mass of empirical formula
Assuming the molar mass of acetic acid is approximately 60.052 g/mol, we can calculate the molecular formula:
- Molecular formula = 60.052 g/mol / 30.026 g/mol
The result is approximately 2, which means the molecular formula is two times the empirical formula.
Therefore, the molecular formula of acetic acid is C2H4O2.
To determine the empirical formula and molecular formula of acetic acid (CH3CO2H), we need to understand the difference between the two:
1. Empirical Formula: It represents the simplest whole number ratio of atoms in a compound.
2. Molecular Formula: It represents the actual number of atoms of each element present in a molecule.
To find the empirical formula:
Step 1: Identify the elements and their respective atoms in the compound. In this case, we have carbon (C), hydrogen (H), and oxygen (O).
Step 2: Determine the mole ratio by dividing the number of moles of each element by the smallest number of moles among them. To do this, we need to know the molar masses of carbon, hydrogen, and oxygen.
The molar masses are:
- Carbon (C): 12.01 g/mol
- Hydrogen (H): 1.01 g/mol
- Oxygen (O): 16.00 g/mol
Step 3: Calculate the moles of each element in acetic acid. From the formula CH3CO2H, we have 2 carbon (C) atoms, 4 hydrogen (H) atoms, and 2 oxygen (O) atoms.
Moles of C:
2 atoms of C * (12.01 g/mol) = 24.02 g/mol
Moles of H:
4 atoms of H * (1.01 g/mol) = 4.04 g/mol
Moles of O:
2 atoms of O * (16.00 g/mol) = 32.00 g/mol
Step 4: Find the smallest number of moles among the elements. In this case, it is 4.04 g/mol for hydrogen (H).
Step 5: Calculate the mole ratio by dividing each element's moles by the smallest number.
Moles of C: 24.02 g/mol / 4.04 g/mol = 5.94
Moles of H: 4.04 g/mol / 4.04 g/mol = 1.00
Moles of O: 32.00 g/mol / 4.04 g/mol = 7.92
Since we cannot have fractional parts in an empirical formula, we need to round these numbers to their nearest whole numbers.
The empirical formula for acetic acid (CH3CO2H) is therefore C2H4O2.
To find the molecular formula:
Step 1: Determine the molar mass of the empirical formula by adding up the molar masses of all the atoms.
- Carbon (C): 12.01 g/mol * 2 = 24.02 g/mol
- Hydrogen (H): 1.01 g/mol * 4 = 4.04 g/mol
- Oxygen (O): 16.00 g/mol * 2 = 32.00 g/mol
Total molar mass of the empirical formula C2H4O2 = 60.06 g/mol
Step 2: Calculate the empirical formula mass by comparing the molar mass of the empirical formula with the molar mass of the compound. The molar mass of acetic acid is usually provided or can be calculated by adding up the molar masses of each element in the molecular formula.
Let's suppose the molar mass of acetic acid is 120.12 g/mol for this example.
Empirical Formula Mass: 60.06 g/mol
Molar Mass of Acetic Acid: 120.12 g/mol
Step 3: Calculate the whole-number multiple by dividing the molar mass of the compound by the empirical formula mass.
120.12 g/mol / 60.06 g/mol = 2
The whole-number multiple is 2. Multiply the subscripts in the empirical formula by this number to get the molecular formula.
Molecular Formula = 2 * C2H4O2 = C4H8O4
Therefore, the empirical formula of acetic acid is C2H4O2, and its molecular formula is C4H8O4.