Unit 6: The MoleNote: Most of this unit will involve solving

problems mathematically, with many examples done in class on the board.

Page 79

= Particles = Molecules Atoms Formula Units

One mole (mol) is the amount of a pure substance that contains

6.02 x 1023 particles.

One mole (mol) is the amount of a pure substance that contains

6.02 x 1023 particles.In honor of the first scientist

to calculate its value,this number is called:

One mole (mol) is the amount of a pure substance that contains

6.02 x 1023 particles.In honor of the first scientist

to calculate its value,this number is called:Avogadro's Number

Molar mass: the total atomic mass of an element or compound in grams

Molar mass: the total atomic mass of an element or compound in grams

Synonyms for molar mass: - molecular mass - formula mass - formula weight

For any element or compound:

For any element or compound:1 mole = molar mass

For any element or compound:

1 mole = molar mass = 6.02 x 1023

! ! ! ! ! ! ! ! ! ! ! ! ! ! particles

For any element or compound:

1 mole = molar mass = 6.02 x 1023

! ! ! ! ! ! ! ! ! ! ! ! ! ! particles*

! ! ! ! ! ! ! ! * atoms, molecules, ! ! ! ! ! ! ! ! ! ! or formula units

Mole Conversions

Mole Conversions

mass ⇄ mole ⇄ particles

Mole Conversions

mass ⇄ mole ⇄ particles(use dimensional analysis!)

See Page 80

Section 7.3 i) Calculating molar massii) Mole-mass conversions

Page 230Percent composition:the percent by mass of each element in a compound.

Practice:What is the percent composition of water?

What is the percent composition of magnesium chloride?

Section 7.4 Determining Chemical Formulas

Empirical formula:the smallest whole-number ratio of atoms in a compound.

Practice:1. Determine the empirical formula of a compound composed of: 81.82% carbon 18.18 % hydrogen

1. Determine the empirical formula of a compound composed of:

81.82% carbon 18.18 % hydrogen (assume a 100-gram sample!)

Note:If mole ratio is within +/-0.1 of a whole

number, round to that number.

If not, multiply by 2/2, 3/3, etc., to obtain a whole-number ratio.

2. Determine the empirical formula of a compound composed of:

68.4% chromium 31.6% oxygen

3. Determine the empirical formula of a compound composed of:

26.6% sulfur 53.2% oxygen 20.2% magnesium

4. Determine the empirical formula of a compound composed of:

9.61g oxygen 7.33g magnesium 0.61g hydrogen?

4. Determine the empirical formula of a compound composed of: 9.61g oxygen 7.33g magnesium 0.61g hydrogen. What is its name?

Molecular formula: the actual number of atoms in a compound.

Molecular formula: the actual number of atoms in a compound…

Molecular formula: the actual number of atoms in a compound... It will be a whole-number multiple of the empirical formula (1, 2, etc…).

Practice 1:The empirical formula of a compound is: C3H4N2.

Practice 1:The empirical formula of a compound is: C3H4N2. What is its molecular formula if the molar mass has been determined to be 204.2 g/mol?

Practice 2:i. Determine the empirical formula of a compound composed of: 40.29% boron 7.51% hydrogen 52.20% nitrogen

WarmUp:i. Determine the empirical formula of a compound composed of: 40.29% boron 7.51% hydrogen 52.20% nitrogenii. If the molar mass of the compound is 80.51g, what its molecular formula?

Pages 231-232The Formula of a Hydrate

Hydrate: An ionic compound that has a specific number of water molecules bound within its crystal structure.

Hydrate: A compound that has a specific number of water molecules bound to its atoms.

Prefixes mono, di, tri, etc. are used to indicate the number of water molecules contained in the hydrate formula.

Examples

Hydrate ------->AnhydrateHeating

Anhydrate: A hydrate that has had its water molecules removed.

Anhydrate: A hydrate that has had its water molecules removed.(aka “desiccant,” a drying agent that absorbs water from the air)

=See Dry Lab Practice Worksheet=