Enter the chemical formula of the substance and the number of atoms for each element present.
0 g/mol
Understanding Molecular Mass Calculation
Molecular mass, also known as molecular weight, is the sum of the atomic masses of all atoms in a molecule. It is a fundamental concept in chemistry used to determine the mass of a given substance or to relate mass to the number of moles. The molecular mass is typically expressed in grams per mole (g/mol) or atomic mass units (amu).
The Calculation Process
To calculate the molecular mass of a compound, you need to follow these steps:
Identify the Chemical Formula: Determine the correct chemical formula for the substance. This formula indicates which elements are present and how many atoms of each element are in one molecule of the compound.
Find Atomic Masses: Look up the atomic mass of each element present in the compound from the periodic table. Atomic masses are usually given in atomic mass units (amu). For calculations involving moles, these values are numerically equivalent to the molar mass in grams per mole (g/mol).
Multiply by Atom Count: For each element, multiply its atomic mass by the number of atoms of that element present in the molecule (as indicated by the subscript in the chemical formula).
Sum the Masses: Add together the results from step 3 for all elements in the compound. This total sum is the molecular mass of the compound.
The formula for molecular mass (M) can be represented as:
M = Σ (n_i * A_i)
Where:
M is the molecular mass.
Σ denotes summation.
n_i is the number of atoms of the i-th element in the molecule.
A_i is the atomic mass of the i-th element.
Common Atomic Masses (Approximate)
Here are some approximate atomic masses for common elements (in g/mol):
Hydrogen (H): 1.01 g/mol
Carbon (C): 12.01 g/mol
Nitrogen (N): 14.01 g/mol
Oxygen (O): 16.00 g/mol
Sodium (Na): 22.99 g/mol
Chlorine (Cl): 35.45 g/mol
Potassium (K): 39.10 g/mol
Calcium (Ca): 40.08 g/mol
Sulfur (S): 32.07 g/mol
Use Cases
Molecular mass calculations are essential in various scientific and industrial applications, including:
Stoichiometry: Calculating the amount of reactants and products in chemical reactions.
Solution Preparation: Determining the mass of a solute needed to create a solution of a specific concentration.
Chemical Analysis: Identifying unknown substances based on their mass properties.
Pharmaceuticals: Formulating medications and understanding drug dosages.
Materials Science: Designing and analyzing new materials.
Example Calculation: Water (H₂O)
To calculate the molecular mass of water (H₂O):
Hydrogen (H): Atomic mass ≈ 1.01 g/mol. There are 2 hydrogen atoms. Contribution = 2 * 1.01 = 2.02 g/mol.
Oxygen (O): Atomic mass ≈ 16.00 g/mol. There is 1 oxygen atom. Contribution = 1 * 16.00 = 16.00 g/mol.
Total Molecular Mass = 2.02 g/mol + 16.00 g/mol = 18.02 g/mol.
Example Calculation: Glucose (C₆H₁₂O₆)
To calculate the molecular mass of glucose (C₆H₁₂O₆):
Carbon (C): Atomic mass ≈ 12.01 g/mol. There are 6 carbon atoms. Contribution = 6 * 12.01 = 72.06 g/mol.
Hydrogen (H): Atomic mass ≈ 1.01 g/mol. There are 12 hydrogen atoms. Contribution = 12 * 1.01 = 12.12 g/mol.
Oxygen (O): Atomic mass ≈ 16.00 g/mol. There are 6 oxygen atoms. Contribution = 6 * 16.00 = 96.00 g/mol.
Total Molecular Mass = 72.06 g/mol + 12.12 g/mol + 96.00 g/mol = 180.18 g/mol.