What is the molar mass of acetaminophen, C8H9NO2? Show calculations.
The Correct Answer and Explanation is:
To calculate the molar mass of acetaminophen (C8H9NO2), we sum the molar masses of each element present in the compound, based on the number of atoms of each element.
Step 1: Identify the elements and their quantities
Acetaminophen has the molecular formula C8H9NO2. This means:
- 8 carbon (C) atoms
- 9 hydrogen (H) atoms
- 1 nitrogen (N) atom
- 2 oxygen (O) atoms
Step 2: Find the atomic masses
From the periodic table, the approximate atomic masses of the elements are:
- Carbon (C): 12.01 g/mol
- Hydrogen (H): 1.008 g/mol
- Nitrogen (N): 14.01 g/mol
- Oxygen (O): 16.00 g/mol
Step 3: Calculate the molar mass
Now, we calculate the molar mass by multiplying the atomic masses of each element by the number of atoms of that element in the formula:Molar mass of acetaminophen=(8×12.01)+(9×1.008)+(1×14.01)+(2×16.00)\text{Molar mass of acetaminophen} = (8 \times 12.01) + (9 \times 1.008) + (1 \times 14.01) + (2 \times 16.00)Molar mass of acetaminophen=(8×12.01)+(9×1.008)+(1×14.01)+(2×16.00)
Breaking it down:
- 8×12.01=96.08 g/mol8 \times 12.01 = 96.08 \, \text{g/mol}8×12.01=96.08g/mol
- 9×1.008=9.072 g/mol9 \times 1.008 = 9.072 \, \text{g/mol}9×1.008=9.072g/mol
- 1×14.01=14.01 g/mol1 \times 14.01 = 14.01 \, \text{g/mol}1×14.01=14.01g/mol
- 2×16.00=32.00 g/mol2 \times 16.00 = 32.00 \, \text{g/mol}2×16.00=32.00g/mol
Now, summing all these values:96.08+9.072+14.01+32.00=151.162 g/mol96.08 + 9.072 + 14.01 + 32.00 = 151.162 \, \text{g/mol}96.08+9.072+14.01+32.00=151.162g/mol
Step 4: Round the result
The molar mass of acetaminophen is approximately 151.16 g/mol.
Explanation
The molar mass is the sum of the masses of the atoms in one mole of the compound. Acetaminophen’s molar mass, as calculated above, tells us that one mole of acetaminophen weighs about 151.16 grams. This calculation is important because it allows chemists to determine how much of the compound is needed for a given amount of substance in moles, which is crucial for stoichiometric calculations in reactions.
