Post on 22-Feb-2016
description
• Chemical Formulas• The Mole • One-Step Molar Conversions
February 24, 2014
• Calculator• Periodic Table• A good attitude about math
Materials
• 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)
Chemical Formulas
• The mass of one molecule, formula unit, or ion.
• Calculate by adding atomic masses together from the periodic table.
• Units: amu (atomic mass unit)
Formula Mass
• Mass H + Mass Cl• 1.0079 + 35.453 = 36.4069 amu
Example: HCl
• 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: NH4NO3
• 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).
Example: PO43-
And now: MOLES
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)
Avogadro’s number
How did they come up with 6.02 x 1023 anyway?
• 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.
• 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
Chemical Formulas
• 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
Molar Mass
• 2(Mass H) + Mass S + 4(Mass O)• 2(1.0079) + 32.066 + 4(15.999)• 98.0178 g/mol
Example: H2SO4
• 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
Example: Ca(NO3)2
Molar Conversions
Mass ingrams
Amount inmoles
Divide by the molar mass
Multiply by the molar mass
• Start with: g• 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 moles are in 2.0 g calcium chloride?
• Start with: moles• 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
Example: How many grams are in 1.5 mol potassium iodide?
Amount inmoles
Number of particles
• Formula unit• Molecule• Ion• Atom
Multiply by Avogadro’s #
Divide by Avogadro’s #
Molar Conversions
• Start with: mol• 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 formula units are in 6.0 mol calcium bromide?
• Start with: molecules (particles)• End with: moles• Math: divide by Avogadro’s number
• 5.0 x 1022 molecules = 0.083 mol• 6.02 x 1023 molecules/mol
• Calculator Help: Use the EE button • 6.02 x 1023 = 6.02EE23
Example: How many moles are in 5.0 × 1022 molecules H2?