Mole Calculations

1. Mole Calculations

2. Mole Calculations A graduated cylinder holds 25.4 cm3 of mercury. If the density of mercury at 25 oC is 13.534 g / cm3, how many moles of mercury are in the cylinder? How many atoms of mercury are there? HINT: Volume of solids/liquids and moles are not directly connected. You must first use the density to convert the volume to a mass, and then derive the quantity of mercury, in moles, from the mass. Finally, the number of atoms is obtained from the number of moles. g cm3 mol g atoms mol x x x Volume, cm3 Mass, g Moles Atoms use density use molar mass use Avogadro’s number Kotz & Treichel, Chemistry & Chemical Reactivity, 3rd Edition , 1996, page 93

3. A B C g cm3 mol g atoms mol x x x Volume, cm3 Mass, g Moles Atoms use density use molar mass use Avogadro’s number A Therefore, the volume of mercury is found to be equivalent to 344 g of mercury. . 13.534 g Hg 1 cm3 Hg 25.4 cm3 Hg = 344 g Hg B Knowing the mass, you can now find the quantity in moles. . 1 mol Hg . 200.6 g Hg 344 g Hg = 1.71 mol Hg Finally, because you know the relation between atoms and moles (Avogodro’s number), you can now find the number of atoms in the sample. C . 6.02 x 1023 atoms Hg . 1 mol Hg 1.71 mol Hg = 1.03 x 1024 atoms Hg Kotz & Treichel, Chemistry & Chemical Reactivity, 3rd Edition , 1996, page 93

4. Formation of Ammonia