2 Stoichiometry Definition: The proportional relationship between two or more substances during a chemical reactionBased on one amount of a substance in a chemical equation, you will be able to calculate the amount of any other substance in a reaction.
3 Substance A (Have) Substance B (Looking For) MOLES MOLES Mass Mass DensityDensityMolarMassMolarMassVolumeVolumeBalancedChemicalEquation22.4 L/mol at STPMOLESMOLES22.4 L/mol at STPAvogadro’sNumberAvogadro’sNumberAtomsAtomsSubstance A(Have)Substance B(Looking For)
4 Problems Involving Mass What mass of NH3 can be made from 1221g H2 and excess N2?N2 + 3H2 2NH3First, write what you knowMass of H2 = 1221g H2Molar Mass of H2 = 2.02 g/mol (this can not be your limiting significant figure)Mass of NH3 = ?g NH3Molar Mass of NH3 = g/mol
5 = Write your mathematical equation 6867 g NH3 X Start with what you were givenCancel unitsUse the balanced chemical equation1 mol H22 mol NH317.04 g NH3=XXX1221g H21 mol NH32.02 g H23 mol H26867 g NH3
6 Problems Involving Particles (Atoms) How many grams of C5H8 form from 1.89x molecules of C5H12? (Answer is 214g C5H8)C5H12 (l) C5H8 (l) + 2H2 (g)Write what you knowAtoms of C5H12 = 1.89x 1024 moleculesAvogadro’s Number = 6.022x 1023 molecules/molMolar Mass of C5H8 = g/molMass of C5H8 = ? g
7 Write your mathematical equation Start with what you were givenCancel unitsUse the balanced chemical equation1 mol C5H121 mol C5H868.13 g C5H81.89x 1024 molecules C5H12XXX1 mol C5H121 mol C5H86.022x 1023 molecules C5H12214 g C5H8
8 Problems Involving Volume What volume of H3PO4 forms when 56mL POCl3 completely react? (density of POCl3 = 1.67 g/mL; density of H3PO4 = 1.83 g/mL)POCl3 (l) + 3H2O (l) H3PO4 (l) + 3HCl (g)Write what you knowVolume POCl3 = 56mL POCl3Density of POCl3 = 1.67 g/mLMolar Mass of POCl3 = g/molMolar Mass of H3PO4 = g/molDensity of H3PO4 = 1.83 g/mLVolume of H3PO4 = ? mL
9 Write your mathematical equation Start with what you were givenCancel unitsUse the balanced chemical equation1.67 g POCl31 mol POCl31 mol H3PO498.00 g H3PO41 mL H3PO456 mL POCl3XXXXX1 mol H3PO41.83 g H3PO41 mL POCl3g POCl31 mol POCl3= 33mL H3PO4