MOLE (mol)
    The mole is the SI unit for amount of a substance.

    The mole is the quantity of a substance which contains as many individual units (e.g. moleucles,
    formula units, atoms) as there are atoms in exactly 0.012 kg (12 g) of carbon-12.

    The number of units in a mole is 6.022 x10²³ and is often referred to as Avogadro's number.

    One mole of carbon-12 contains 6.022 x10²³  atoms of carbon-12.

    One mole of water contains 6.022 x10²³  molecules of water.

    The mole is defined so that a sample of an element with a mass equal to its atomic mass in
    grams contains Avogadro's number of that element.

    There are 22.99 g of sodium in one mole of sodium metal.  There are 10.81 g of boron in one
    mole of elemental boron.

    The mass of one mole in grams of a substance is called the molar mass.

EXAMPLE 1
How many moles are there in a 11.5 gram sample of sodium metal?
[0.500 mol Na]
 
 
 
 
 

EXAMPLE 2
What is the mass of 0.125 mol of boron?
[1.35 g B]
 
 
 
 
 
 

MOLAR MASS OF COMPOUNDS
The molar mass of a compound is equal to the sum of the atomic masses of the atoms
composing the compound.

EXAMPLE 3
What is the molar mass of H₂O?
[18.02 g/mol]
 
 
 
 
 
 

EXAMPLE 4
What is the mass of 19.70 mol of water?
[355.0 g H₂O]
 
 
 
 
 
 

EXAMPLE 5
How many moles are in a 1.00 gram sample of of potassium sulfate, K₂SO₄?
[5.74 x 10^-3 mol K₂SO₄]
 
 
 
 
 

Some examples of hydrates are:

    CuSO₄ ^.5 H₂O   Copper(II) sulfate pentahydrate

    NiSO₄ ^.6 H₂O    Nickel(II) sulfate hexahydrate

    AlK(SO₄)₂ ^.12 H₂O  Aluminum potassium sulfate dodecahydrate

When determining the molar mass for a hydrate the waters of hydration must be included.

EXAMPLE 6
What is the molar mass of copper(II) sulfate pentahydrate, CuSO₄^.5 H₂O?
[249.72 g/mol]