1. Mole Calculations

2. Volume, cm 3 Mass, gMolesAtoms use densityuse molar mass use Avogadro’s number g cm 3 mol g atoms mol xxx A graduated cylinder holds 25.4 cm 3 of mercury. If the density of mercury at 25 o C is 13.534 g / cm 3, 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. Kotz & Treichel, Chemistry & Chemical Reactivity, 3 rd Edition, 1996, page 93

3. Therefore, the volume of mercury is found to be equivalent to 344 g of mercury. Volume, cm 3 Mass, gMolesAtoms use densityuse molar mass use Avogadro’s number g cm 3 mol g atoms mol xxx. 13.534 g Hg 1 cm 3 Hg 25.4 cm 3 Hg =344 g Hg 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.. 6.02 x 10 23 atoms Hg. 1 mol Hg 1.71 mol Hg =1.03 x 10 24 atoms Hg A ABC B C Kotz & Treichel, Chemistry & Chemical Reactivity, 3 rd Edition, 1996, page 93

4. Formation of Ammonia