Question 1
Multiple choiceHard1 markEqual masses of iron and glucose are compared. Count particles as Fe atoms in iron and C₆H₁₂O₆ molecules in glucose. Which row correctly compares the numbers of particles and the total numbers of atoms?
| Element | C | H | O | Fe |
|---|---|---|---|---|
| Ar | 12.01 | 1.01 | 16.00 | 55.85 |
Show answer and explanation
Answer: D. For equal sample masses, particle number is inversely proportional to relative particle mass. Mr(C₆H₁₂O₆) = 6(12.01) + 12(1.01) + 6(16.00) = 180.18 (no units), which is greater than Ar(Fe) = 55.85; therefore, the iron sample has more particles. Each glucose molecule contains 24 atoms, so total atom numbers are proportional to 24/180.18 for glucose and 1/55.85 for iron. The glucose sample has more atoms overall.
A: treats relative mass as directly proportional to particle number; its conclusion about total atoms is correct.
B: gets the particle comparison right but overlooks the 24 atoms in each glucose molecule.
C: uses direct proportionality for particle number and fails to account for the 24 atoms per glucose molecule when comparing total atoms.
Remember: equal masses contain more particles of the substance with the lower relative particle mass, but total atom counts also depend on atoms per particle.