Limiting Reactant Chemical Equations

Limiting Reactant (LR) Reactant (starting item) that LIMITS the amount of products produced LR – will be used entirely up first

Excess Reactant (ER) “Left Over” starting substance ER – Remainder

Chemically – Apply Stoich to Determine LR and ER

Step 1 Balance Equation

Step 2 Convert both given reactant quantities ( from problem ) into ONE OF THE PRODUCTS (doesn’t matter which one you choose) Therefore, you will have 2 conversions

Step 3 Reactant the produces the SMALLEST amount of product is LR

Step 4 Reactant the IS NOT LR, is the Excess Reactant (ER)

Step 5 Using LR, convert to all other products produced (if asked)

Step 6 Calculating ER left over: Use LR and covert into ER mass (going from one reactant to another reactant)

Step 6.1 Subtract starting ER amount (initially given in problem) from the amount converted using LR Converted ER – Starting (given) ER = Amount of Excess Reactant Left Over

Percent Yield Fancy Term for figuring out how big something was screwed up in the experiment. Crunched numbers say you are suppose to get 100 grams and the experiment shows you got 77 grams, percent yield shows how “OFF” you are

Percent Yield (simple terms) Percentage: What I actually Got/What I was supposed to get (x100)

Percent Yield (scientific definition)

Step 7 Calculate Percent Yield = Actual/Theoretical x 100 Careful in figuring out what is the actual and what is the theoretical (READ PROBLEM CAREFULLY)