Chemical Formulas The Mole One-Step Molar Conversions February 24, 2014
Calculator Periodic Table A good attitude about math Materials
Covalent:C 8 H 18 – Octane – # Carbon: 8 – # Hydrogen: 18 Ionic:Al 2 (SO 4 ) 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 = amu Example: HCl
Mass N + 4(Mass H) + Mass N + 3(Mass O) (1.0079) (15.999) = amu OR 2(Mass N) + 4(Mass H) + 3(Mass O) 2(14.007) + 4(1.0079) + 3(15.999) = amu Example: NH 4 NO 3
Mass P + 4(Mass O) (15.999) = 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: PO 4 3-
And now: MOLES
The Mole 1 mole = 6.02 × 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 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 x particles per mole.
Covalent:C 8 H 18 – Octane – Moles Octane: 1 – Moles Carbon: 8 – Moles Hydrogen: 18 Ionic:Al 2 (SO 4 ) 3 – Aluminum Sulfate – Moles aluminum sulfate: 1 – Moles Aluminum: 2 – Moles Sulfur: 3 – Moles Oxygen: 12 Chemical Formulas
Mass of one mole (6.022 × ) 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) (15.999) g/mol Example: H 2 SO 4
Mass Ca + 2(Mass N) + 6(Mass O) (14.007) + 6(15.999) = g/mol OR Mass Ca + 2((Mass N) + 3(Mass O)) ((14.007) + 3(15.999)) = g/mol Example: Ca(NO 3 ) 2
Molar Conversions Mass in grams Amount in moles 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, CaCl (35.453) = g/mol 2.0 g CaCl 2 = mol 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 = g/mol 1.5 mol x g/mol = g Example: How many grams are in 1.5 mol potassium iodide?
Amount in moles 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 =3.612 x f. units Calculator Help: Use the EE button EE = x x = 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 molecules = mol 6.02 x molecules/mol Calculator Help: Use the EE button 6.02 x = 6.02EE23 Example: How many moles are in 5.0 × molecules H 2 ?