Study Guides/Chemistry/Which substance has the greatest molecular mass
Study Guide · Chemistry

Which Substance Has the Greatest Molecular Mass?

In Chemistry, Molecular Mass (or Molar Mass) is the sum of the atomic masses of all atoms in one molecule. Simple compounds like water (18 g/mol) or salt (58.5 g/mol) have small values. But certain biological molecules have staggeringly large molecular masses.

Question (Click to Flip)

What is the molecular mass of CO₂?

Answer

CO₂ = C + 2O = 12 + (2×16) = 12 + 32 = 44 g/mol

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Key Facts

Titin, a muscle protein, is the largest known protein molecule and has a molecular mass of approximately 3,000,000 g/mol (3 megadaltons)!

Simple Compounds vs. Giant Molecules

  • Water (H₂O): 18 g/mol
  • Salt (NaCl): 58.5 g/mol
  • Glucose (C₆H₁₂O₆): 180 g/mol
  • Haemoglobin (protein in blood): ~64,500 g/mol
  • DNA molecule: Can reach billions of g/mol!

Why do Proteins and DNA have huge molecular masses?

Proteins and DNA are polymers — giant chain molecules made by linking thousands or millions of smaller units (monomers) together.

  • A protein is a chain of hundreds of amino acids
  • A single strand of human DNA contains over 3 billion nucleotide units

Each link in the chain adds to the total molecular mass, which is why these biological molecules dwarf simple compounds.

In Exam Context

For a typical MCQ in Class 11 Chemistry asking 'which has the greatest molecular mass' among simple compounds:

  • Compare: SO₂ (64), CO₂ (44), H₂O (18), HCl (36.5)
  • SO₂ (64 g/mol) would have the greatest mass in this set.

Formula: Molecular Mass = sum of (atomic mass × number of atoms) for each element.

Questions and Answers

What is the molecular mass of CO₂?+

CO₂ = C + 2O = 12 + (2×16) = 12 + 32 = **44 g/mol**

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