Which of the following samples contains the greatest number of atoms?
Correct answer: D. 1 mole of ammonia, NH3
- A. 1 mole of helium gas
- B. 1 mole of oxygen gas, O2
- C. 1 mole of water, H2O
- D. 1 mole of ammonia, NH3
Explanation
Every sample contains one mole of molecules, so the answer depends on the number of atoms in each molecule: helium has one, oxygen two, water three and ammonia four. One mole of ammonia therefore contains 4 x 6.02 x 10^23 atoms, more than any of the others. Confusing moles of molecules with moles of atoms is exactly the error this question is designed to expose.
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About Moles and Avogadro's Number
The mole connects the microscopic number of particles with measurable mass, using Avogadro's number, 6.022 × 10²³ particles per mole. Questions involve molar mass, conversion between mass, moles and particles, percentage composition, empirical and molecular formulas, and distinguishing atoms, molecules, ions and formula units.
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