Chapter 6 Chemical Quantities

How you measure how much?  You can measure mass, or volume, or you can count pieces.  We measure mass in grams.  We measure volume in liters.  We count pieces in MOLES.

Moles  Defined as the number of carbon atoms in exactly 12 grams of carbon-12.  1 mole is 6.02 x particles.  Treat it like a very large dozen  6.02 x is called Avagadro’s number.

Representative particles  The smallest pieces of a substance.  For a molecular compound it is a molecule.  For an ionic compound it is a formula unit.  For an element it is an atom.

Types of questions  How many oxygen atoms in the following? CaCO 3 Al 2 (SO 4 ) 3

Types of Questions  How many ions in the following? CaCl 2 NaOH Al 2 (SO 4 ) 3

Measuring Moles  Remember relative atomic mass?  The amu was one twelfth the mass of a carbon 12 atom.  Since the mole is the number of atoms in 12 grams of carbon-12,  the decimal number on the periodic table is also the mass of 1 mole of those atoms in grams.

Gram Atomic Mass  The mass of 1 mole of an element in grams.  grams of carbon has the same number of pieces as grams of hydrogen and grams of iron.  We can write this as g C = 1 mole  We can count things by weighing them.

What about compounds?  in 1 mole of H 2 O molecules there are two moles of H atoms and 1 mole of O atoms  To find the mass of one mole of a compound determine the moles of the elements they have Find out how much they would weigh add them up

What about compounds?  What is the mass of one mole of CH 4 ?  1 mole of C = g  4 mole of H x 1.01 g = 4.04g  1 mole CH 4 = = 16.05g  The Gram Molecular mass of CH 4 is 16.05g  The mass of one mole of a molecular compound.

Gram Formula Mass  The mass of one mole of an ionic compound.  Calculated the same way.  What is the GFM of Fe 2 O 3 ?  2 moles of Fe x g = g  3 moles of O x g = g  The GFM = g g = g

Molar Mass  The generic term for the mass of one mole.  The same as gram molecular mass, gram formula mass, and gram atomic mass.

Examples  Calculate the molar mass of the following and tell me what type it is.  Na 2 S N2O4N2O4 CC

Examples  Ca(NO 3 ) 2  C 6 H 12 O 6  (NH 4 ) 3 PO 4

Using Molar Mass Finding moles of compounds Counting pieces by weighing

Molar Mass  The number of grams of 1 mole of atoms, ions, or molecules.  We can make conversion factors from these.  To change grams of a compound to moles of a compound.

For example  How many moles is 5.69 g of NaOH?

For example  How many moles is 5.69 g of NaOH?

For example  How many moles is 5.69 g of NaOH? l need to change grams to moles

For example  How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH

For example  How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH l 1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g

For example  How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH l 1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g l 1 mole NaOH = g

For example  How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH l 1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g l 1 mole NaOH = g

For example  How many moles is 5.69 g of NaOH? l need to change grams to moles l for NaOH l 1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g l 1 mole NaOH = g

Examples  How many moles is 4.56 g of CO 2 ?  How many grams is 9.87 moles of H 2 O?

Examples  How many molecules in 6.8 g of CH 4 ?  4.9 x molecules of C 6 H 12 O 6 weighs how much?