Counting Atoms By Their Mass • The mass of an atom is called its ________________ • Atomic mass provides a means to count atoms by measuring the mass of a sample • The atomic mass unit is derived from the 12C isotope • (1 amu = 1.6605402x10-24 g) & (1 amu = 1 particle) • We can use this as a conversion factor to convert between these quantities. • Example: What is the atomic mass of silver? Counting Molecules By Their Masses • The molecular mass allows counting of molecules by mass • The molecular mass is the sum of the atomic masses of the all the atoms in the compound’s formula • Strictly speaking, ionic compounds do not have a molecular mass we describe an analogous quantity- the formula mass to cover all possibilities Example: What is the formula/molecular mass of smelling salts, (NH4)2CO3?Learning Check 1. What is the atomic mass of Pb? 2. What is the molecular mass of cocaine, C17H21NO4? 3. What is the formula mass of
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