Answer: All contain equal molecules.
- A 18 g of H<sub>2</sub>O, since water has the lowest molar mass listed
- B 44 g of CO<sub>2</sub>, since carbon dioxide has the highest molar mass listed
- C 32 g of O<sub>2</sub>, since oxygen gas has an intermediate molar mass
- D All contain equal molecules
Correct answer: D. All contain equal molecules
Explanation: Each sample is exactly 1 mole of its substance, so each contains 6.022 x 10<sup>23</sup> molecules.
Mass connects to moles via molar mass, and moles connect to particle count via Avogadro's number or to gas volume via the 22.4 L/mol rule at STP.
Concept context
The mole is chemistry's counting unit. Learn to relate mass, volume, and number of particles using Avogadro's number and molar mass, the foundation of all stoichiometry and reaction calculations.