WAEC Chemistry 2010 Paper

Concept:Compare the total moles of atoms in each gas by using the molecular formula and the number of moles given.Explanation:The number of atoms in a sample depends on both the amount of gas in moles and the number of atoms present in each molecule.For neon, $\mathrm{Ne}$ is monatomic, so $6$ moles of neon contain $6 \times 1 = 6$ moles of atoms.For oxygen, one molecule of $\mathrm{O}_2$ has $2$ atoms, so $3$ moles of oxygen contain $3 \times 2 = 6$ moles of atoms.For chlorine, one molecule of $\mathrm{Cl}_2$ has $2$ atoms, so $2$ moles of chlorine contain $2 \times 2 = 4$ moles of atoms.For ethane, one molecule of $\mathrm{C}_2\mathrm{H}_6$ has $2 + 6 = 8$ atoms, so $1$ mole of ethane contains $1 \times 8 = 8$ moles of atoms.Since $8$ moles of atoms is greater than $6$, $6$, and $4$ moles of atoms, ethane has the highest number of atoms at s.t.p.Answer:D. 1 mole of ethane