Answer: one.
- A one
- B zero
- C 100
- D the number of components
Correct answer: A. one
Explanation: Mole fraction is the ratio of moles of a component to the total moles; summing them over all components always gives exactly 1.
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.