February 24, 2014

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February 24, 2014. Chemical Formulas The Mole One-Step Molar Conversions. Materials. Calculator Periodic Table A good attitude about math. Chemical Formulas. Covalent: C 8 H 18 Octane # Carbon: 8 # Hydrogen: 18 Ionic: Al 2 (SO 4 ) 3 Aluminum Sulfate # Aluminum: 2 # Sulfur: 3

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February 24, 2014
• Chemical Formulas
• The Mole
• One-Step Molar Conversions
Materials
• Calculator
• Periodic Table
• A good attitude about math
Chemical Formulas
• Covalent: C8H18
• Octane
• # Carbon: 8
• # Hydrogen: 18
• Ionic: Al2(SO4)3
• Aluminum Sulfate
• # Aluminum: 2
• # Sulfur: 3
• # Oxygen: 12
• (4 O’s in each sulfate, 3 sulfates in the compound, 3 x 4 = 12)
Formula Mass
• The mass of one molecule, formula unit, or ion.
• Calculate by adding atomic masses together from the periodic table.
• Units: amu (atomic mass unit)
Example: HCl
• Mass H + Mass Cl
• 1.0079 + 35.453 = 36.4069 amu
Example: NH4NO3
• Mass N + 4(Mass H) + Mass N + 3(Mass O)
• 14.007 + 4(1.0079) + 14.007 + 3(15.999) =
• 80.0426 amu
• OR
• 2(Mass N) + 4(Mass H) + 3(Mass O)
• 2(14.007) + 4(1.0079) + 3(15.999) =
• 80.0426 amu
Example: PO43-
• Mass P + 4(Mass O)
• 30.974 + 4(15.999) = 94.97 amu
• The charge does not affect the mass because the mass of an electron is so very small that it is negligible (able to be ignored).
The Mole
• 1 mole = 6.02 × 1023 particles
• It is the number of atoms in exactly 12.0 g of carbon-12
• It is used the same way as:
• A dozen (12)
• A pair (2)
• A score (20)

How did they come up with 6.02 x 1023anyway?
• If you divide the charge on a mole of electrons by the charge on a single electron you obtain a value of Avogadro’s number of 6.02214154 x 1023 particles per mole.
Chemical Formulas
• Covalent: C8H18
• Octane
• Moles Octane: 1
• Moles Carbon: 8
• Moles Hydrogen: 18
• Ionic: Al2(SO4)3
• Aluminum Sulfate
• Moles aluminum sulfate: 1
• Moles Aluminum: 2
• Moles Sulfur: 3
• Moles Oxygen: 12
Molar Mass
• Mass of one mole(6.022 × 1023) of any molecule, formula unit, or ion.
• Calculate by adding atomic masses together from the periodic table.
• Units: g/mol
Example: H2SO4
• 2(Mass H) + Mass S + 4(Mass O)
• 2(1.0079) + 32.066 + 4(15.999)
• 98.0178 g/mol
Example: Ca(NO3)2
• Mass Ca + 2(Mass N) + 6(Mass O)
• 40.078 + 2(14.007) + 6(15.999) =
• 164.086 g/mol
• OR
• Mass Ca + 2((Mass N) + 3(Mass O))
• 40.078 + 2((14.007) + 3(15.999)) =
• 164.086 g/mol
Molar Conversions

Amount in

moles

Mass in

grams

• Divide by the molar mass
• Multiply by the molar mass
Example: How many moles are in 2.0 g calcium chloride?
• End with: moles
• Math: divide by molar mass
• Molar mass of calcium chloride, CaCl2
• 40.078 + 2(35.453) = 110.984 g/mol
• 2.0 g CaCl2= 0.018 mol

110.984 g/mol

Example: How many grams are in 1.5 molpotassium iodide?
• End with: g
• Math: multiply by molar mass
• Molar mass of potassium iodide, KI
• 39.098 + 126.90 = 165.998 g/mol
• 1.5 mol x 165.998 g/mol = 248.997 g
Molar Conversions
• Number of particles
• Formula unit
• Molecule
• Ion
• Atom

Amount in

moles

Multiply by

Divide by

• End with: formula units (particles)
• Math: multiply by Avogadro’s number
• 6.0 mol x 6.02 x 1023 =3.612 x 1024 f. units
• Calculator Help: Use the EE button
• EE = x 10
• 6.02 x 1023 = 6.02EE23
Example: How many moles are in 5.0 × 1022 molecules H2?