Catalyst
• Calculate the number of grams of carbon
dioxide produced when 1.2 x 1024 particles of
oxygen gas (O2) are reacted.
2 C2H2 + 5 O2 ---> 4 CO2 + 2 H2O
End
Test Next Monday/Tuesday!
Lecture 4.6 – Percent Yield
Today’s Learning Targets
• LT 4.9 – I can hypothesize and calculate the
percent yield for a given chemical reaction.
What is percent yield?
I. Percent Yield
• Stoichiometry tells us what should happen for
a reaction. This is the theoretical yield.
• We predict using stoichiometry conversions
• The amount that a reaction actual produces is
known as the actual yield.
How do we calculate percent yield?
I. Calculating the Percent Yield
• Percent yield can be calculated by the
equation:
actual yield
´ 100% = Percent yield
theoretical yield
• Calculate the theoretical yield using
stoichiometry.
• Often, you experiment to obtain the actual
yield.
Class Example
• I perform the following reaction:
2H2 + O2  2H2O
and I predict that I will produce 18 g of H2O. If
I actually produce 16 g of H2O, then what is
my percent yield?
Class Example
• I perform the following reaction:
4 KI + K4(CrO4) 2  2 I2 + 2 K2O + K4(CrO3) 2
I react 332 g of KI with excess K4(CrO4)2. If I
actually produce 228.6 g of I2, what is my
percent yield for the reaction?
Percent Yield Lab
• Please read through the lab handout that you
picked up when you entered the classroom.
• Note areas of confusion.
• Once finished discuss with your table what
each person at your table will be doing once
the lab has begun.
Lab Work Time
Lab Debrief
• Make sure to complete the calculations and
post-lab questions before next
Thursday/Friday.
• Where do you think error was introduced in
this lab?
• What do you think were sources of error for
this lab? How did it contribute to your
percent yield?
What does our percent yield mean?
I. What Percent Yield Means
• Percent yield is often lower than 100%
because of error
• 2 types of error:
– Human error – Mistakes that we make during an
experiment
– Experiment Design Error – There are often error
associated with the way that we design an
experiment
• Every experiment has sources of error
SUMMARIZE
Closing Time
• Lab Report Discussion due
• Review Packet worth 5 extra credit point on
exam grade!