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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=
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