Mole of Molecules

1 mole Ag 107.87 grams Ag 1870 grams Ag 1 × 1 mole Ag 107.87 grams Ag 17.3 mole Ag 201 grams Hg 1 mole Hg 0.004 moles Hg 1 ×^{201 grams Hg} 1 mole Hg 0.8 grams Hg CHARACTERISTICS OF ATOMS DOE-HDBK-1015/1-93 Fundamentals of Chemistry CH-01 Rev. 0 Page 10 Example 1: A silver bar has a mass of 1870 grams. How many moles of silver are in the bar? Solution: Since the atomic mass of silver (Ag) is 107.87 amu, one mole of silver has a mass o f 107.87 grams. Therefore, there is one mole of Ag per 107.87 grams of Ag or . There are 1870 grams of silver. Example 2: Mercury (Hg) is the only metal that exists as a liquid at room temperature. It isused in thermometers. A thermometer contains 0.004 moles of mercury. How many grams of mercury are in the thermometer? Solution: Since the atomic mass of Hg is 201 amu, one mole of Hg has a mass of 201 grams of Hg or . There are 0.004 moles of Hg. Mole of Molecules The mass of a mole of molecules ofa substance is the molecular mass expressed in grams. For example, an oxygen molecule (O) has a molecular mass equivalent to 32.0 grams because each 2 oxygen atom has a molecular mass of 16.0 grams. (Recall that to obtain the molecular mass, the atomic masses of all atoms that appear in the formula are added.) If the atomic masses of the carbon and four hydrogen atoms in methane, CH , are added, the total is 16 amu. Therefore, one 4 mole of CH has a mass of 16 grams. The mass of a mole of molecules is called the molar mass 4 or gram molecular weight(GMW).