A student has equal-volume samples of three gases. All the gases are at the same temperature and pressure. If the three gases are O₂, CO₂, NH₃, which sample contains the largest number of atoms?

Question

Quizplus · Accepted Answer

The number of atoms in a sample is determined by the number of moles of the gas and Avogadro's constant (6.02×1023 mol-1). By comparing the molecular formulas, we can see that the samples contain 1 mole each of the gases, which means they all contain the same number of moles. However, the number of atoms in each mole is different due to the different compositions of the molecules. O₂ contains 15 atoms per mole (1 sulfur, 2 boron, 12 oxygen) CO₂ contains 14 atoms per mole (1 carbon, 1 sulfur, 2 boron, 12 oxygen) NH₃ contains 16 atoms per mole (1 nitrogen, 1 sulfur, 1 boron, 13 oxygen) Therefore, NH₃ has the largest number of atoms per mole and, consequently, per equal-volume sample.

A Student Has Equal-Volume Samples of Three Gases