Which of the following contains maximum no. of atoms ?

Question

Question

This question was previously asked in

NPCIL Stipendiary Trainee (Category-II) Official Paper (Held On: 11 Jun 2019)

Answer 1

The correct answer is 18 gm H₂O

Key Points

Molar Mass: The molar mass of H₂O (water) is approximately 18 g/mol, which means 1 mole of water weighs 18 grams.
Number of Molecules: 1 mole of H₂O contains Avogadro's number (6.022 × 10²³) of molecules.
Atoms in a Molecule: Each H₂O molecule consists of 3 atoms (2 hydrogen atoms and 1 oxygen atom).
Total Atoms Calculation: Therefore, 18 g of H₂O contains 3 × Avogadro's number of atoms, which equals approximately 18.066 × 10²³ atoms.
Comparison: 18 g of H₂O has more atoms compared to the same mass of O₂, CO₂, or CH₄ due to the lower molar mass and higher atom count per molecule.

Additional Information

Avogadro's Number: This is a fundamental constant, 6.022 × 10²³, representing the number of constituent particles (usually atoms or molecules) in 1 mole of a substance.
Molar Mass: The molar mass is the mass of one mole of a given substance (chemical element or chemical compound) expressed in grams per mole (g/mol).
Water (H₂O): It is composed of two hydrogen atoms and one oxygen atom, making it a triatomic molecule with a molecular weight of 18 g/mol.
Oxygen (O₂): As a diatomic molecule, the molar mass of O₂ is 32 g/mol, implying fewer moles and atoms in 18 grams of O₂ compared to H₂O.
Carbon Dioxide (CO₂): With a molar mass of 44 g/mol, 18 grams of CO₂ corresponds to fewer moles and thus fewer atoms than the same mass of H₂O.
Methane (CH₄): Methane has a molar mass of 16 g/mol, and 18 grams of CH₄ also results in fewer total atoms than the same mass of H₂O due to the molecular composition.