chemistry brooks

OBJECTIVE

1.     Define mole and molar mass

2.     Calculate the molar mass of a comppund

MOLE

·       Is the amount of a substance, usually HUGE

·       SI unit for an amount

·       One MOLE= 6.022 x 10²³ pieces (602200000000000000000000)

·       It is known as avogadros number

·       One Mole of a substance is equal to a number

·       Example:

o   If I have one dozen baseballs, how many baseballs do I have? 12

o   If I have one dozen eggs, how many eggs to I have? 12

o   A dozen is a numeric measure of an amount.

o   The same amount of something is not going to have the same mass

EXAMPLE

1 Mole of mm’s=

·       Would fit into 256,454,000 Semi Truck Trailers  (2.3481x10¹⁵)

·       IF the truck trailers were connected it would go around the earth 1 billion times

Molar Mass

·       Does not affect significant figures

·       Units are grams per mole

·       Mass of a substance in grams

Calculating Molar Mass

            The sum of atomic masses of each element in a compound multiplied by their individual subscripts

·       Example:

o   AL₂S₃

§  AL= 26.98 x 2= 53.96       (take the atomic mass x subscript)

§  S= 32.07 x 3 = 96.21        (take the atomic mass x subscript)

                                                  150.17g/mol        (add them both up)

·       Calcium Phosphate

o    Ca3(PO₄)₂

§  CA = 40.09 x 3 = 120.27

§  P = 30.97 x 2 = 61. .00

§  O = 16.00 = 128.00

      310. 21 g/mol

PRACTICE

·       BaBr₂

·       N₂O₅

o    N = 14.01 x 2 = 28. 02

o    O= 16.00 x 5 = 80.00

§  108. 02 g/mol

·       C₇H₁₆

·       Zn(OH)₂

o    ZN= 65.39 x 1 = 65.39

o    O₂ = 16.00 x 2 =

o    H₂= 1.01 x 2 =

·       Silver Nitrate Ag NO₃^-1

o    Ag= 107.87 x 1 = 107.87

o    N=  14.01 x 1 = 14.01

o    O= 16.00 x 3 = 48.00

§  169.88 g/mol

·       Hexane