Molar Mass Molecular Weight and Elemental Composition Calculator
Accurately calculate molar mass, percent composition, and stoichiometry for any chemical compound.
Chemical Compound Analyzer
Enter a valid chemical formula (case sensitive, e.g., 'Co' is Cobalt, 'CO' is Carbon Monoxide).
Please enter a valid chemical formula.
Molar Mass / Molecular Weight
0.00
g/mol
Total Atoms
0
Distinct Elements
0
Most Abundant (by Mass)
N/A
Elemental Composition
Element
Symbol
Atomic Mass (g/mol)
Count
Total Mass (g/mol)
Mass %
Mass Percentage Breakdown
What is a Molar Mass Molecular Weight and Elemental Composition Calculator?
A molar mass molecular weight and elemental composition calculator is an essential tool for chemists, students, and researchers. It automates the complex process of determining the mass of one mole of a substance (molar mass) and analyzing the percentage contribution of each element within a chemical compound (elemental composition).
Whether you are balancing chemical equations in stoichiometry or preparing solutions in a laboratory, knowing the exact molecular weight is critical. This tool eliminates manual calculation errors by using precise atomic weights from the periodic table to parse complex formulas, including those with parentheses and polyatomic ions.
Common misconceptions often confuse "molar mass" with "molecular weight." While they are numerically identical for practical purposes, molar mass is expressed in grams per mole (g/mol), whereas molecular weight is a dimensionless quantity or expressed in Daltons (Da). This calculator provides the value in g/mol, which is the standard unit for laboratory calculations.
Molar Mass Formula and Mathematical Explanation
The calculation of molar mass involves summing the atomic masses of all constituent atoms in a molecule. The formula can be expressed mathematically as:
Molar Mass = Σ (Atomic Mass of Element_i × Number of Atoms of Element_i)
To find the elemental composition (percent by mass), the calculator uses the following ratio for each element:
% Composition = (Total Mass of Element / Total Molar Mass of Compound) × 100%
Key Variables
Variable
Meaning
Unit
Typical Range
Atomic Mass
Mass of a single atom of an element
g/mol (or amu)
1.008 (H) to 294 (Og)
Subscript
Number of atoms of a specific element
Integer
1 to 1000+
Molar Mass
Total mass of one mole of the substance
g/mol
2.016 to 100,000+ (polymers)
Practical Examples (Real-World Use Cases)
Example 1: Glucose (C₆H₁₂O₆)
Scenario: A biochemist needs to prepare a glucose solution and requires the exact molar mass to weigh out the correct amount.
Input: C6H12O6
Calculation:
Carbon (C): 12.011 × 6 = 72.066 g/mol
Hydrogen (H): 1.008 × 12 = 12.096 g/mol
Oxygen (O): 15.999 × 6 = 95.994 g/mol
Total Molar Mass: 180.156 g/mol
Result: The biochemist knows that 1 mole of glucose weighs approximately 180.16 grams.
Example 2: Calcium Nitrate (Ca(NO₃)₂)
Scenario: An agricultural chemist is calculating nitrogen content in fertilizer.
How to Use This Molar Mass Molecular Weight and Elemental Composition Calculator
Enter the Chemical Formula: Type the formula into the input field. Ensure you use correct capitalization (e.g., use "Cl" for Chlorine, not "cl" or "CL").
Handle Groups: Use parentheses for groups of atoms, such as "(OH)2" or "(NH4)2SO4".
Click Calculate: Press the "Calculate Molar Mass" button.
Review Results:
The large number at the top is the total molar mass.
The table breaks down how much each element contributes to the total mass.
The pie chart visualizes the mass percentage of each element.
Copy Data: Use the "Copy Results" button to paste the data into your lab notebook or report.
Key Factors That Affect Molar Mass Results
While the calculation seems straightforward, several factors influence the accuracy and application of molar mass data in a financial or scientific context (e.g., purchasing reagents or calculating yields).
Isotopic Abundance: Standard atomic weights are averages based on natural abundance. Enriched isotopes will have different molar masses.
Hydration State: Many chemicals absorb water from the air (hygroscopic). A formula like CuSO₄ is different from CuSO₄·5H₂O (pentahydrate). Always account for water molecules in the formula.
Purity of Reagents: In practical applications, reagents are rarely 100% pure. Calculations must often be adjusted for purity percentages (e.g., 98% pure).
Significant Figures: The precision of the result depends on the precision of the atomic masses used. This calculator uses standard IUPAC values to 3-4 decimal places.
Case Sensitivity: Incorrect capitalization changes the meaning. "Co" is Cobalt (mass ~58.9), while "CO" is Carbon Monoxide (mass ~28.0).
Cost Implications: In industrial chemistry, the "cost per mole" is a vital metric derived from molar mass and bulk price ($/kg). Higher molar mass often implies higher transport costs per mole of active ingredient.
Frequently Asked Questions (FAQ)
1. What is the difference between Molar Mass and Molecular Weight?
Molar mass is the mass of one mole of a substance (g/mol), while molecular weight is the mass of a single molecule (amu or Daltons). Numerically, they are usually treated as the same value.
2. Can this calculator handle hydrates?
Yes, but you must enter them as part of the formula. For example, for Copper(II) Sulfate Pentahydrate, enter "CuSO4(H2O)5" or sum the parts manually if dot notation is not supported by the parser logic.
3. Why is capitalization important?
Chemical symbols are case-sensitive. "Pb" is Lead, but "PB" would be interpreted as Phosphorus and Boron. Always follow the periodic table standard.
4. How are parentheses handled?
The calculator distributes the subscript outside the parenthesis to all elements inside. For example, in Ca(NO3)2, the '2' applies to both N and O3.
5. Does this tool calculate molarity?
No, this tool calculates Molar Mass. Molarity requires volume data. You can use the result from this calculator as an input for a Molarity calculation.
6. What atomic weights are used?
We use the standard atomic weights from the IUPAC periodic table, averaged for natural isotopic abundance.
7. Is this calculator useful for stoichiometry?
Absolutely. Converting grams to moles is the first step in almost all stoichiometry problems, and this tool provides the conversion factor (g/mol).
8. Can I calculate the mass of a protein?
Theoretically yes, if you type the full formula (e.g., C400H620N100O120S1). However, for macromolecules, specialized protein mass calculators are often preferred due to formula length.