The molecular mass of propane-1,2-diol is 76.1 amu . Calculate the molecular mass of propane-1,3-diol, an isomer of propane-1,2-diol.
The Correct Answer and Explanation is:
Correct Answer:
The molecular mass of propane-1,3-diol is 76.1 amu.
Explanation:
Propane-1,3-diol and propane-1,2-diol are isomers, meaning they have the same molecular formula but different arrangements of atoms. Since molecular mass depends only on the types and numbers of atoms in a molecule, isomers always have identical molecular masses.
Let’s verify this by calculating the molecular formula and then computing the molecular mass step by step.
Step 1: Determine the molecular formula of propane-1,3-diol
Both propane-1,2-diol and propane-1,3-diol have the molecular formula:
C₃H₈O₂
Explanation:
- “Propane” means a chain of 3 carbon atoms.
- “Diol” means there are two hydroxyl (OH) groups.
- The numbers 1,2 and 1,3 just tell us where the OH groups are located on the carbon chain, not how many atoms are present.
So, the atom counts are:
- Carbon (C) = 3
- Hydrogen (H) = 8
- Oxygen (O) = 2
Step 2: Calculate the molecular mass
Now we add up the atomic masses of each atom:
- Carbon: 3 × 12.01 = 36.03 amu
- Hydrogen: 8 × 1.008 = 8.064 amu
- Oxygen: 2 × 16.00 = 32.00 amu
Total molecular mass:
36.03 + 8.064 + 32.00 = 76.094 amu, which rounds to 76.1 amu
Final Point:
Since propane-1,2-diol and propane-1,3-diol are structural isomers with the same molecular formula, their molecular masses must be equal.
Thus, the molecular mass of propane-1,3-diol is 76.1 amu.