Explain why a 5.0 gram sample of water would not have the same number of particles in it as a 5.0 gram sample of salt?

Answer 1

The reason is because the number of particles is not dependent on the mass or weight of the material, but rather is dependent on the number of moles of material. Comparing water (H2O) to salt (NaCl), we have...

5.0 g H₂O x 1 mol H₂O / 18 g H2O = 0.278 moles H₂O

5.0 g NaCl x 1 mol NaCl / 58.5 g NaCl = 0.085 moles NaCl

Since there are more moles of H₂O in 5.0 g than there are in 5.0 g of NaCl, there will be more particles of H₂O