Catalyst
• For the reaction:
C6H12O6 (aq)  C2H5OH (aq) + CO2 (g)
1.Balance the above reaction
2.How many particles of CO2 form when 92 g of
C2H5OH are produced?
End
Test This Tuesday!
Lecture 4.5 – 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 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 of error
SUMMARIZE
White Board Races
Questions
1. If I predict that I will produce 100 g of CH3OH
and I actually produce 57 g of CH3OH, then what
is my percent yield?
2. If I predict that I will produce 25 g of CH2O and I
actually produce 15 g of CH2O, then what is my
percent yield?
3. I run the following reaction in lab:
CS2 + 2 O2  C + 2 SO2
If I react 64 g of O2 with excess CS2 and I actually
produce 10 g of C, then what is my percent yield?
Closing Time
• Lab Report Introduction due Tuesday!
• Review Packet worth 5 extra credit point on
exam grade!