Download labprac.09B

SCH 4U
INDEPENDENT LAB PRACTICAL EVALUATION
NAME:
Introduction: More consumers are drinking energy drinks, but this practice could affect the oral health of
consumers
who sometimes daily rely on these drinks for an extra boost. In this lab, you are going to
analyze the
acid content of drink mixes and related concepts in order to draw a conclusion about
the effects of
powdered drink mixes.
PART A
a)
Summarize the key points in:
Popular Energy Drinks Cause Tooth Erosion, Study Shows. ScienceDaily. Retrieved June 9, 2009, from
http://www.sciencedaily.com /releases/2008/03/080312125606.htm
Sports Drink Consumption Can Cause Tooth Erosion, Study Finds. ScienceDaily. Retrieved June 9, 2009, from
http://www.sciencedaily.com /releases/2009/04/090403122016.htm
b)
Use chemical equations to explain the effect of sports drinks on teeth.
c)
Explain the term “buffering capacity” used in the article and how it applies to soft drinks.
d)
Review buffer solutions in your text and the section and practice questions. When you are ready, you will
complete an in-class assignment on buffers (2-3 questions).
PART B
Purpose:
To prepare and standardize a strong base
To determine the concentration of acid in powdered drink mixes by titrating it with a standardized
base.
3)
To calculate the pH of the endpoint of a strong base-weak acid titration
Note: All sections must be completed to obtain full marks!!!!!
Reference:
1)
2)
van Kessel et al. (2003). Chemistry 12. Nelson: Toronto
Refer to pp.627-629 (“Quantitative Titration”) for a detailed procedure.
Introduction: Potassium and sodium hydroxide cannot be obtained in a pure form and the solid is only 85 % pure. The
KOH or NaOH solution must first be standardized - its concentration must be determined by titrating it with
an acid of a known concentration or a solid acid standard.
Procedure: Standardization of base
Include your calculations. Briefly describe the steps you followed and the materials used.
Observations:
Data for titration of KOH/NaOH:
rough
trial #1
mass of KHC8H4O4
________
__________ __________ ___________
final volume base
_____
______ _______
_______
initial volume base
_____
______ _______
_______
volume of base used
_____
______ _______
_______
1.
Determine concentration of base. SHOW ALL WORK!!!!
trial #2
trial #3
PART C –
Purpose:
Procedure:
1.
a.
To determine the concentration of total acid in powdered drink mixes
Have your method checked by your teacher to determine the concentration of citric acid in a standard
solution. Brief explanation and data table needed. This is a check to test the precision and accuracy
of your
proposed method for determining the total acid content in your standard solution.
rough
trial #1
trial #2
trial #3
mass of citric acid used
_____
______
_______
_______
final volume base
_____
______
_______
_______
initial volume base
_____
______
_______
_______
volume of base used
_____
______
_______
_______
total volume in flask
______
______
_______
_______
measured pH at end-point
______
______
_______
_______
b.
Calculations/accuracy
2.
a.
Develop your procedure for determining total acid content in powdered drink mixes. Brief
explanation and observation table needed.
rough
trial #1
trial #2
trial #3
volume of solution used
_____
______
_______
_______
final volume base
_____
______
_______
_______
initial volume base
_____
______
_______
_______
volume of base used
_____
______
_______
_______
b.
3.
Calculations/accuracy
Explain why thymol blue is the best indicator for the reaction. Write the equation for the reaction of the salt with
water to demonstrate.
4.
Calculate the pH of the solution in your flask at end-point. Compare to your measured pH and explain differences.
You
will need an equation, ICE table, and use of K. Research how to calculate pH for polyprotic acids in order to
accurately
determine the pH.
5.
Complete lab for preparing standard thiosulfate solution.
6.
mix.
Determine the concentration of ascorbic acid in the standard citric and ascorbic solution and in the powdered drink
See website and http://www.outreach.canterbury.ac.nz/chemistry/documents/vitaminc_iodine.pdf for
information. Brief explanation and observation table needed.
additional
7.
Draw a conclusion about the acid content of powdered drink mixes and the effect on dental health. Include a
discussion
of sources of error.
Evaluation:
Any
All lab notes will stay in class.
You must have the teacher check each part as you complete it. Your work will only be marked in class!!!!
tasks not completed next Wednesday, will not be marked.
All titrations require a brief description of the procedure, data tables, calculations and error calculations.
You will be working independently and must do our own work.