91Ó°ÊÓ

In general, why must we weigh a sample in order to determine the number of atoms it contains?

What is a mole? Why do chemists need to use the concept?

If \(1.00 \mathrm{~mol}\) of \(\mathrm{LiCl}\) has a mass of \(42.394 \mathrm{~g}\), what is the average mass of \(1 \mathrm{LiCl}\) formula unit in atomic mass units?

If one formula unit of \(\mathrm{CuCl}_{2}\) has an average mass of \(134.5 \mathrm{amu}\), what is the mass of \(1.00 \mathrm{~mol}\) of \(\mathrm{CuCl}_{2}\) ?

If \(2.01 \times 10^{23}\) molecules of a substance have a mass of \(12.0 \mathrm{~g}\), what is the molar mass of the substance?

If the molar mass of a substance is \(98.09 \mathrm{~g} / \mathrm{mol}\), what is the mass of \(3.01 \times 10^{23}\) molecules of the substance?

Calculate the number of moles in \(10.0 \mathrm{~g}\) of the following substances. (a) \(\mathrm{KHCO}_{3}\) (c) Se (b) \(\mathrm{H}_{2} \mathrm{~S}\) (d) \(\mathrm{MgSO}_{4}\)

Calculate the number of moles in \(100.0 \mathrm{~g}\) of each of the following compounds. (a) \(\mathrm{SO}_{2}\) (c) \(\mathrm{BaSO}_{4}\) (b) \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) (d) \(\mathrm{KAl}\left(\mathrm{SO}_{4}\right)_{2}\)

Calculate the moles of the following substances. (a) \(72.2 \mathrm{~g} \mathrm{~K}_{2} \mathrm{SO}_{4}\) (c) \(2.82 \mathrm{~kg}\) magnetite, \(\mathrm{Fe}_{3} \mathrm{O}_{4}\) (b) \(160.0 \mathrm{mg}\) oxycodone, (d) \(5.00 \mu \mathrm{g}\) sucrose, \(\mathrm{C}_{18} \mathrm{H}_{21} \mathrm{NO}_{4}\) \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\)

Which element, Mo, Se, Na, or Br, contains the most moles of atoms in a \(1.0-\mathrm{g}\) sample?