CEM 141 Stoichiometry

what is stoichiometry

• the relationship between the macroscopic and molecular level

• can calculate how much product can be produced in a reaction

• tells the relationship between any two components in a reaction

what is the mole

• it allows us to connect from the molecular level to the observable macroscopic level

  • can easily translate between the molecular and macroscopic scale

• 6.022 × 10²³ “things”

• it’s just a big number

• the mass of 1 mole of any substance is its formula mass in grams

• molar mass = mass in grams of 1 mole

describe the stoichiometry map

grams A → moles A → moles B → grams B

• g/mol

• stoichiometric ratio from the balanced equation

• g/mol

describe the mole → number conversions

• use avogadro’s number

• 6.022 × 10²³ blah

• 1 mole of anything will always be 6.022 × 10²³ of that thing

  • so when comparing the # of molecules in 1 mole of different substances they will all have the same # of molecules

what is the limiting reagent/reactant and how do you calculate it

• the amount of one of the reagents, which limits how much product can be formed

• it will run out first

• do NOT compare masses directly

• do NOT compare moles directly

• DO calculate the amount of product possible from each reactant and whichever produces the least product is the limiting reactant

how to find percent yield

% yield = (actual/theoretical) x 100

aka… % yield = (given/our calculation) x 100

• should never get over 100%…. or that close tbh, it’s rare