Unit 4 The Mole and Molar Mass
Read pages HW: WS: Lewis Dot and Naming Acids Mole Worksheet: Number 2, #1-3 Quiz: Thursday or Friday Feb. 7 th or 8 th Lesson 1 Unit 4
MEASURING MATTER 3 ways to measure things: count: 1 dozen = 12 apples mass: 1 dozen = 2 kg of apples volume: 1 dozen = 0.20 bushel (for typical wicker basket)
MASS OF A SINGLE ATOM To calculate the mass of ONE atom of carbon: 1 amu = one proton or one neutron = 1.66 x g mass of one C atom = x g IMPOSSIBLE, IMPRACTICLE!
MASS OF MANY ATOMS One atom cannot be weighed. Can we weigh many atoms and still determine relative masses of different atoms? …
HELIUM ATOM VS. NITROGEN ATOM 1400 amu400 amu100 atoms 140 amu40 amu10 atoms 28 amu8 amu2 atoms N = 14 amuHe = 4 amu1 atom Mass ratio ( 2 : 7 ) is always the same!
AVOGADRO’S NUMBER number of atoms whose mass in grams = mass of one atom in amu example: carbon 1 carbon atom = amu ?? atoms = grams of carbon ANSWER: 6.02 x atoms!
We call this number of “things” one MOLE: 6.02 x “things” = 1 mole just like 12 “things” = 1 dozen AVOGADRO’S NUMBER
“THINGS”: REPRESENTATIVE PARTICLES 1 mole = 6.02 x representative particles 1 mole carbon = 6.02x10 23 atoms 1 mole CO 2 = 6.02x10 23 molecules 1 mole NaCl = 6.02x10 23 formula units
1 atom of hydrogen = 1.01 amu 6.02x10 23 atoms of H = 1.01 grams 1 mole of H = 1.01 grams usually written as: 1.01 g/mole This number is called the MOLAR MASS of hydrogen. THE MOLE AND MOLAR MASS
MOLAR MASS carbon: MM = g/mole g = 1 mole = 6.02x10 23 atoms magnesium: MM = g/mole g = 1 mole = 6.02x10 23 atoms 1 mole = same number of atoms = different number of grams
MOLAR MASS What is the molar mass of sulfur? g/mole What is the molar mass of SO 3 ? g/mole What is the molar mass of NaCl? g/mole
dow.html?pid=803http:// dow.html?pid=803