2. How many chlorine atoms are there in a sample that contains 2.67 mol of Cl?

Answer 1

Chlorine usually exists as a diatomic molecule, Cl₂. At STP, one mole of gas contains Avrogadro's number of molecules. Our sample of gas here contains 2.67 moles of Chlorine. The number of molecules in the sample is then 2.67 x 6.022 x 10²³ molecules/mol = 1.607 x 10²⁴ molecules. But the question asked is "how many atoms are present?" Because each molecule of Chlorine contains two atoms, the answer is 2 x 1.607 x 10²⁴ atoms are present = 3.22 x 10²⁴ atoms.