DEIONIZED WATER Experiment. EDTA Titration of Zinc in an unknown sample Objective

Experiment. EDTA Titration of Zn2+ in an unknown solution and a supplement tablet
Modified 09/2014
Experiment. EDTA Titration of Zinc in an unknown sample
Objective: In this experiment, you will find the concentration of zinc in a zinc supplement tablet by EDTA titration,
with the assumption that EDTA reacts 1:1 with metal (Zn2+) ions.
***USE ONLY
DEIONIZED WATER
(NOT DISTILLED WATER!)THROUGHOUT THE ENTIRE EXPERIMENT***
Equipment
Chemicals
150-mL Erlenmeyer flask (3)
50-mL Buret
Ring-stand and hardware
400-mL Beaker
Buffer (pH 10.0):
10.0-mL Vol Pipette
100-mL grad cylinder
250-mL Volumetric Flask
Hot plate
Eriochrome Black T:
Unknown: Zinc supplement table and Zinc unknown solution
Submit a clean 250-mL volumetric flask to the instructor so that an unknown
zinc solution may be issued. Your name, section number, and your locker
number should be written legibly on this flask. Note that the flask must be
turned in at least 1 lab period before you plan to do the experiment, so that
the lab tech will have time to prepare the unknown.
Safety and Waste Disposal
1. Empty all titrated Ca and Zn solutions into the proper Hazardous Waste Bottle for this experiment.
2. When completely done with the experiment mix any remaining EDTA titrant and any remaining Ca stock solution
together in a large beaker. Pour in the labeled waste container in the hood. The two solutions are slightly basic and
slightly acidic, respectively; when mixed, they will be near neutral. There are also no toxic chemicals present.
Discussion:
Zinc makes up about 75 ppm (0.0075%) of the Earth’s
crust, making it the 24th most abundant element. Zinc
is necessary for the functioning of more than 300
different enzymes and plays a vital role in a large
number of biological processes. Zinc is involved in
numerous aspects of cellular metabolism. It is required
for the catalytic activity of approximately 100
enzymes and it plays a role in immune function, protein
synthesis , wound healing, DNA synthesis, and cell
division. Zinc also supports normal growth and
development during pregnancy, childhood, and
adolescence and is required for proper sense of taste
and smell. A daily intake of zinc is required to maintain
a steady state because the body has no specialized
zinc storage system.1
Zinc is an essential mineral that is naturally present in some foods, added to others, and available as a dietary
supplement. Zinc is also found in many cold lozenges and some over-the-counter drugs sold as cold remedies.
The current RDAs for zinc are listed in Table 1.
EDTA is also used in foods. Certain enzymes are responsible for food spoilage. EDTA is used to remove metal ions from
these enzymes. It is used to promote color retention in dried bananas, beans, chickpeas, canned clams, pecan pie filling,
frozen potatoes and canned shrimp. It is used to improve flavor retention in canned carbonated beverages, beer, salad
dressings, mayonnaise, margarine, and sauces. It inhibits rancidity in salad dressings, mayonnaise, sauces and spreads.
This experiment is an example of a classic titrimetric analysis. Classical methods of analysis such as titrimetric and
gravimetric analyses are usually capable of very high precision and accuracy - typically on the order of + 0.1% or better,
if done properly. However, there is always a tradeoff. Classical methods are slower and much less sensitive than
modern instrumental methods of analysis such as atomic absorption spectroscopy, gas and liquid chromatography, and
mass spectrometry.
In a titration, an accurately known mass of sample is dissolved in aqueous solution, often with some sort of chemical
treatment such as acid-digestion of solid samples, and diluted with high purity water to an accurately known volume.
Then, an accurately known volume of the sample solution, called an aliquot, is pipetted into a titration vessel and the
analyte of interest is carefully titrated with a standardized solution of an appropriate titrant to the endpoint or
equivalence point of the titration. To do this, you need to know when you reach the endpoint. This is often accomplished
by means of an indicator that undergoes a color change at the endpoint.
From the volume and molarity of the titrant, one can then calculate the number of moles of titrant used. From the
known stoichiometry of the reaction between the titrant and the analyte, one can calculate the moles of the analyte
followed by the mass and/or molarity of the analyte. With appropriate calculations, one can then determine the
concentration and/or total mass of the analyte in the original sample to complete the analysis.
This titration is known as a complexometric or chelometric titration
because the titrant (ligand) reacts with the analyte (metal ion) to form a
complex (chelate). A chelate is a ligand that has two or more sites that
bind to the central ion. EDTA [ethylenediaminetetraacteic acid,
C10H16N2O8, (HOOCCH2) 2N-CH2CH2-N(CH2COOH)2, MW = 292.24
g/mol, often symbolized by H4Y] is an excellent chelating agent. It forms
very strong 1:1 complexes with almost every divalent and trivalent metal ion
depending on solution conditions.
The reaction is as follow, ignoring charges for the moment,
EDTA + M D MEDTA
Although it is an equilibrium, the reaction lies very far to the right. The equilibrium formational constants, Kf, are on
the order of 108 - 1025 depending on the metal and other conditions.
EDTA itself is a tetraprotic4-acid; it has 4 ionizable protons (usually represented as H4Y) with pKa's = 1.99, 2.67, 6.16,
10.26. In its fully ionized form, Y-4 , the four acetate groups and the lone pairs on the two nitrogen makes it a
hexidentate ligand that wraps itself very tightly around a metal ion. Usually, titrations are performed in basic solution,
roughly pH 8-11.
The fully protonated form, H4Y, is only sparingly soluble in water, so the standard form of EDTA used analytically is
usually the disodium salt Na2H2Y•2H2O (372.24 g/mol), which is much more soluble and available in primary standard
purity, except for a small (about 0.3%) amount of adsorbed water.
Concentrations of metals such as zinc, calcium and magnesium can be determined by titration with a standard solution
of ethylenediamminetetraacetic acid, EDTA. The EDTA is a complexing, or chelating agent used to capture the metal
ions. For example, when calcium in water is bound to EDTA, the water is now softened. The term “soft” water refers to
treated water that cannot precipitate the mineral residues (limescale or soap scum) found in "hard" water, because the
ions now bind EDTA, the chelating agent.
In this lab you will be asked to determine the amount of zinc in a zinc supplement tablet and an unknown solution. EDTA
grabs all the metal ions in the water, not just the Zn2+ ions. This may result in a value that is not truly the
concentration of Zn2+ ions and causes an experimental error of about 1%.
Experiment. EDTA Titration of Zn2+ in an unknown solution and a supplement tablet
Modified 09/2014
Procedure
Skip this step if the EDTA titrant has been prepared for you.
Preparation of EDTA, 0.01 M.
This solution must be prepared at least one day ahead of time, a week is preferable, to ensure that the solute is
completely dissolved. EDTA solutions are prepared at an approximate molarity, and then standardized against a solution
of a primary standard such as CaCO3.
1. Dissolve about 3.8 g of the dihydrate of the disodium salt (Na2H2Y 2H2O) and 0.1 g MgCl2 in approximately 1 L of
deionized water in a large beaker or a 1-L plastic bottle using a magnetic stirrer. A small amount of sodium hydroxide
can be added if there is any difficulty in dissolving the EDTA. Try not to exceed 3.8 g of the disodium salt because
much more than this dissolves only with difficulty.
2. Before use, the EDTA solution should be filtered using a Buchner funnel and suction filtration. Refer to experiment 1
on the operation of a Buchner funnel. [NOTE: Break the suction before you turn off the water flow on the vacuum
aspirator.]
3. Store the solution in a clean, labeled 1-L plastic bottle that has been rinsed with deionized water. Never store
reagent solutions in volumetric flasks.
Ammonia/Ammonium Chloride Buffer Stock Solution, pH 10.
Each titration will require the addition of pH 10 ammonia buffer. The stock buffer solution has been prepared for you,
and you should not have to prepare it. The appropriate quantity (7-8 mL) is dispensed directly into your titration flask
from the plastic Repipet® repetitive dispenser. The buffer should only be added immediately before you titrate an
individual sample. Recipe:
1. Dissolve 64.0 g of ammonium chloride in 600 mL of concentrated ammonia (14.8 M, 28% NH3).
2. Slowly and carefully add 400 mL deionized water with stirring. This should be sufficient for over 120 titrations.
Calcium Standard Solution.
A CaCO3 solution is prepared as a primary standard for Ca and used to standardize the 0.01 M EDTA titrant.
1. Tap out approximately 1 g of predried analytical-reagent-grade CaCO3 in a weighing boat. Accurately weigh (to
within +0.1 mg) approximately a 0.25-g sample by difference into a 150- or 250-mL beaker.
NOTE: NEVER transfer chemicals inside an analytical balance.
2. Add about 25 mL deionized water and then slowly add concentrated HCl dropwise with periodic stirring until the
sample dissolves completely. Then add 2 drops more. Keep the beaker covered during the entire dissolution process.
Mild heating will speed the dissolution.
Do NOT boil; this will spatter the calcium solution and lead to losses.
3. Transfer the solution quantitatively into a 250-mL volumetric flask. Rinse the beaker thoroughly with deionized
water, and carefully dilute to the mark with an eye dropper or with careful use of your wash bottle. Mix thoroughly.
Because this Ca2+ standard solution is used to standardize the EDTA titrant, it must be prepared very carefully so
that you know its exact molarity. Therefore, an exactly known (to ± 0.1 mg) mass of CaCO3 must be weighed out,
dissolved completely, and transferred quantitatively into the 250-mL volumetric flask. This is critical.
Standardization of the EDTA Solution
1. Attach your 50-mL buret to a ringstand, preferably using one with a white ceramic base, and a buret clamp. If the
only ringstands available have black bases, cover the base with a completely white sheet of paper before you titrate a
sample.
2. Open the buret valve and drain it completely into a "waste" beaker. Squirt down the insides with deionized water a
couple of times. If any water droplets remain attached to the inside of the buret, you must thoroughly wash the
buret with soap and a buret brush to remove them. If you leave "reagent spots" in the buret while titrating, the
titration volume will be in error. Squirt down the insides of the buret a couple of times with a mL or two of the EDTA
solution with a medicine dropper to rinse any remaining deionized water out of the buret.
3. Now close the buret valve and over-fill the buret with your standard EDTA solution. Check to see if any air bubbles
are trapped in the tip of the buret. If so, open and close the valve quickly as though you were "squirting" reagent from
the buret into the waste beaker until the bubbles have cleared from the tip. Carefully bring the reagent level to
somewhere between the 0- and 1-mL marks. Do not try to bring the level exactly to the 0.00-mL mark. This is a waste
of time. Rinse the buret tip off with a squirt of deionized water, let it drain, and then touch the tip to the side of the
waste beaker to remove excess water.
4. Pipet 25.00-mL aliquots of your standard Ca2+ solution into each of three or four 250-mL Erlenmeyer flasks. Each
aliquot will thus contain one-tenth of the total CaCO3 that was weighed out to prepare the standard solution.
5. Take each sample to completion before starting the next sample. Read the initial volume on the buret at least twice.
Add 7-8 mL of pH 10 buffer from the Repipet® dispenser, 15 mL of deionized water, and 3 drops of Eriochrome Black
T indicator, immediately prior to titrating a sample. The solution should be a pale pink. Do not add more indicator to
make the solution darker as this can cause problems with the endpoint. Titrate the solution immediately with EDTA
against a white background until the LIGHT PINK solution turns a LIGHT SKY BLUE. Read the final volume at least
twice.
Titrations must be performed swiftly (but carefully) because the NH3 will evaporate to some degree and thus the pH
of the solution will change. In general, the faster the titrations are performed the better the results will be, as long as
the endpoint is not overshot due to excessive haste.
It is advantageous to perform a trial titration to locate the approximate endpoint and to observe the color change. In
succeeding titrations, titrate very rapidly to within about 1 or 2 mL of the endpoint, and then titrate very carefully, a
drop or half-drop at a time, to the endpoint. Near the endpoint, periodically squirt the sides of the flask and the buret
tip and swirl the flask to ensure all the titrant has gotten into the solution in the flask.
The endpoint color change is rather subtle, and sometimes it is slow, so you need to be careful at the end. If you are
having trouble with the endpoint color change, see Note 1 at the end of the report for the preparation of "before" and
"after" flasks.
Calculate the molarity of the EDTA solution from the volume of EDTA used in the titration of each aliquot. The values
(MEDTA and titration volumes) should all agree very closely, to within about +0.4% relative standard deviation. If not,
titrate additional aliquots until better agreement is reached.
Outlying values can always be rejected for cause or one outlying value by using the Q-test.
Analysis of the Zinc Unknown solution
1. Carefully dilute your unknown sample in the 250-mL volumetric flask to the mark with deionized water. Mix
thoroughly.
2. Pipet 25.00-mL aliquots into each of three or four 250-mL Erlenmeyer flasks. Add 15 mL of deionized water, 7-8 mL
of pH 10 buffer, and 3 drops of Eriochrome Black T immediately prior to titrating a sample.
3. Titrate with standardized EDTA until the pink solution turns light blue.
Calculate the milligrams of zinc in the total sample. Remember that each aliquot represents one tenth of the total
sample volume - a 25-mL aliquot titrated out of 250 mL total volume.
Experiment. EDTA Titration of Zn2+ in an unknown solution and a supplement tablet
Modified 09/2014
Titrating the Zinc tablets
The instructions are based on a target of 1 tablet (100mg) of zinc supplement tablet. These tablets have been crushed
to powder to mask their brand identity.
1. You will be given an unknown for a specific brand of zinc supplement. Weigh out about 0.1 grams to the nearest
0.1mg. Place the powder into a clean 250mL Erlenmeyer flask and then add about 30 mL of deionized water, using the
flask volume markings. Heat the contents gently on a warm (not boiling) hot plate if necessary for a few minutes until
the tablet disintegrates. Depending on the tablet, some binders fillers might not dissolved. This is okay as the zinc will
be in solution.
2. Add 7-8 mL of the pH 10 buffer solution and add 3 drops of Eriochrome Black T immediately prior to titrating a
sample.
3. Refill your buret with EDTA solution as necessary. Titrate as previously mentioned above, to the end-point color
change. Repeat until you are confident that you have satisfactory titration results for three (3) tablets.
4. Upon completion of the experiment, discard all solution in a chemical waste bottle and wash out the glassware. Be
sure to dry your buret in the upside-down position.
HAZARDOUS WASTE DISPOSAL
Empty all the Ca and Zn solutions that were titrated into the proper Hazardous Waste Bottle
for this experiment. If you are unsure of the proper container, ASK.
When you are completely done with the experiment, mix any remaining EDTA titrant, Ca standard stock solution, and Zn
unknown solution together the waste container labeled Ca, Zn EDTA in the hood.
IMPORTANT NOTE
1. Eriochrome Black T Indicator. The color change of Eriochrome black T at the endpoint is rather subtle. It is not an
abrupt change from deep red to a dark blue; but rather it is from a light red (or pink) to a pale blue. At least one trial
titration is recommended. (You can always discard a "bad" value when you know there is a definite reason for its being
bad. Make sure you indicate a possible problem in your notebook at the time you observe it.)
If you have trouble distinguishing the endpoint, a "before" and an "after" flask are recommended. Prepare two 250-mL
flasks in a similar manner as were the samples – except do not add the 25 mL of Ca solution. Instead, add a total of
about 80-90 mL of deionized water to approximate the volume of the sample aliquot (25 mL), the volume of EDTA
titrant that would have been titrated into the flask, and the 15 mL of deionized water. Add the indicator and the
ammonia buffer. To one flask (the "before" the endpoint flask) add a few drops of the Ca solution; to the other flask
(the "after" flask) add a small amount of EDTA solution to get just past the color change at the endpoint. Stopper the
flasks and keep them nearby for comparison of the colors. Titrate against a white background for better
discrimination of colors.
Sometimes the Eriochrome black T solution goes bad because of air oxidation. If the endpoints seem very indistinct or
slow to you, try a fresh bottle of indicator. Alternatively, try adding a small amount of solid Eriochrome black T
mixture (1 g indicator ground with 100 g NaCl). A small amount on the end of a spatula is sufficient.
Calculations –
Analysis:
Molarity of Ca2+ standard solution.
The molarity of the Ca2+ standard solution (MCa) is calculated in normal fashion using the molar mass of calcium carbonate (MM
CaCO3) weighed out and the total volume in liters of the standard solution prepared.
1. Convert mass of CaCO3 to moles of Ca.
2. Convert moles of Ca to molarity of Ca2+ using the total volume of the standard solution
Concentration of EDTA solution
The reaction of Ca2+ ions with Na2H2EDTA takes place with a 1:1 stoichiometric ratio:
Ca2+ + Na2H2EDTA
D
CaH2EDTA.
At the end point of the titration, 1-equivalent of Ca2+ reacts with one equivalent of Na2H2EDTA.
1 eqv Ca2+ = 1 eqv Na2H2EDTA; equivalent Ca2+ = [Na2H2EDTA] • Vol EDTA
1. Convert molarity of calcium from the stock solution to moles of calcium. 25-mL aliquot was used in the titration.
2. Convert moles of calcium in the 25 ml aliquot to moles of EDTA based on the end point of the titration.
3. Calculate the concentration of the EDTA titrant based on the volume of the EDTA used to reach the end point.
Mass of zinc in the unknown
The concentration of the zinc in your unknown solution can be determine in the same manner as the concentration of the EDTA
titrant solution was determined above.
1. Calculate the moles of EDTA to reach the equivalent point for the titration of zinc solution based on the volume used for the
titration.
2. Convert of moles of EDTA to moles of zinc.
3. Calculate the moles of zinc to molarity of zinc in the unknown solution.
4. Calculate the mass of zinc in the unknown solution keeping in mind the 250mL volume
5. Calculate the % m:v of the unknown zinc solution.
Mass of zinc in a vitamin supplement
Approximately .100 g of a supplemental tablet was used in this analysis. The tablet was dissolved in 250mL solution. 25-mL of
this solution was used for the complexometric titration.
1. Calculate the moles of EDTA to reach the equivalent point for the titration of zinc tablet based on the volume used.
2. Convert of moles of EDTA to moles of zinc.
3. Calculate the moles of zinc to molarity of zinc in the unknown solution.
4. Convert molarity of zinc in the unknown solution to moles of zinc in the unknown using the dilution factor (250mL volume)
5. Calculate the mass of zinc per 0.100 g of the supplemental table.
6. Calculate the % m:m of zinc in 0.100 g sample.
Statistical Analysis –
1. Report the mean, medium, standard deviations (s), relative standard deviation (RSD), variance (s2) and the 95% confidence
interval for your results.
2. Apply the student’s t test at the 95% confidence interval.
3. Apply a Q-test to any suspected result.
4. Confidence interval = x + t s
n
5. Compare the zinc % concentration of your supplement tablet to the zinc % concentration of the solution. Apply the
Comparison of Means with Student’s t, Case2 (p76) Comparing Replicate Measurements. Do the two unknown samples agree within
the 95% confidence interval?
Experiment. EDTA Titration of Zn2+ in an unknown solution and a supplement tablet
Modified 09/2014
Test for Outlier
Apply a Grubb’s Test and Q-Test for any suspected outliers at 95 % level. See page 83 of text for critical values for 95%
confidence. If your results show an anomalous data then use the Q-test to determine if the result should be rejected.
Q=
(Suspected Value - Nearest Value)
(Suspected Value - Furthest Value)
Table of Data, Results and Statistical Analysis:
EDTA Raw Data
1.
Mass of Ca used to standardize EDTA
2
Volume EDTA at equivalent point when titrating with Ca.
3
Concentration of EDTA standard solution
4
Zinc solution Data
1
Unknown number for zinc solution
2
Volume EDTA during titration of zinc solution
Zinc supplemental tablet Data
1
Unknown number for zinc unknown
2
Mass of zinc tablet used
3
Volume EDTA during titration of zinc tablet
G calc =
| Questionable value - x |
s
EDTA Concentration Results
1. Concentration of EDTA solution
Zinc unknown solution and zinc tablet
1. Unknown number
2. Mass of zinc in the unknown solution
3. % concentration m:v of zinc in the unknown solution
5. Statistical results for solution as indicated below
6. Mass of zinc in the since supplemental tablet
7. % concentration m:m of zinc in the tablet
8. Statistical results for tablets as indicated below
Statistical Analysis
1. Averages and Standard deviations of all results above
2. Variance, RSD and CV of all results above
3. 95% CL for results above
4. Comparison of Student t between solution and tablets
5. Suspected outlier and G and Q test results at 95% level
Discussion (Talking points)The goal of this experiment was to determine the amount of zinc in a single supplement tablet (~100mg) as well as the amount of zinc
in an unknown solution. A discussion of this experiment should include the accuracy and precision of this experiment in all phases of
the experiment, i.e., preparation of EDTA and the standardization process, the preparation of all zinc analytes and the titration
process.
Reference:
1. http://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
2. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium,
Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press,
2001.
.
Sample data table (To be modified).
Sample Unknown # ______
Mass CaCO3 l (g)
Concentration of CaCO3. (M)
EDTA Titration of CaCO3 Std
Buret Volinitial, (ml)
Trial 1
Trial 2
Trial 3
Trial 4*
Buret Volfinal, (ml)
Volume EDTA used, (ml)
Vol EDTA for blank, (ml)
Corrected Vol EDTA, (ml)
Average
Std dev
Variance,
RSD, CV
95% CL
Average
Std dev
Variance,
RSD, CV
95% CL
Average
Std dev
Variance,
RSD, CV
95% CL
Concentration EDTA (M)
* Extra run for outlier
Zinc unknown solution
EDTA Titration Zn solution
Trial 1
Trial 2
Trial 3
Trial 4*
Volume of aliquot Zn solution (mL)
Buret Volinitial, (ml)
Buret Volfinal, (ml)
Volume EDTA used, (ml)
Vol EDTA for blank, (ml)
Mass of Zinc in solution
% m:v Zinc in solution
* Extra run for outlier
Q and G Test for Outline
Mass tablet supplement (g)
EDTA Titration Zn Supplement
Trial 1
Trial 2
Trial 3
Trial 4*
Mass zinc supplement (g)
Buret Volinitial, (ml)
Buret Volfinal, (ml)
Volume EDTA used, (ml)
Vol EDTA for blank, (ml)
Mass of Zinc in supplement
% m:m Zn in 0.100 g supplement
* Extra run for outlier
Q and G Test for Outline
Experiment. EDTA Titration of Zn2+ in an unknown solution and a supplement tablet
EDTA Titration of Zn2+ in an unknown solution and tablet supplement
Modified 09/2014
#
1
CRITERIA (Tentative point distribution - may change depending on experiment)
Quiz / Homework [NONE}
2
Introduction and Procedures
A. Introduction
• Objective of Expt.
• Background information.
• Math relationship used in study.
B. Procedures
• Outline of procedures in Expt.
• Flow chart pictorial of procedures.
• Procedural changes.
• Information (data) to be recorded during experiment. (to be presented in Table form.)
• Safety and disposal information.
This portion of the report should be turned in before the start of lab class (prelab discussion).
Data, Observe., Results and Calc.
C. Data and Observation
• Data in table form. & detailed observations written in the table. All data entry should contain the proper
number of significant figures and units. Data should always be recorded in an organize fashion.
• Balance chemical equations; all chemical reaction which occurred during an experiment should be written
in this section. Then it should also be written in the discussion portion of the report.
This portion of the report should be turned in before you leave the laboratory.
Calculations & Results
D. Calculations
• Sample calculation shown with Excel spreadsheet available with formulas shown.
• Statistical analysis of data and result. x (mean), s (std dev), s2, RSD, CV
3
pts %
E. Results
• Summary of Result(s) in table form.
In this section accuracy of results is very important as well as detailed calculation showing how the result was
obtain. "Unknown" will also be included in this section.
4
5
6
Discussion / Conclusions and Post-Lab Questions
F. Discussion (Talking points)
•What is your final result in this experiment. Are the trial titration to standardize the EDTA solution
consistent with each other? Are the concentration of the zinc in the supplement tablet consistent with
each other. How do the result compare to typical amounts in zinc supplemental tablets? Are the three
trials consistent with each other?
G. Conclusion
• Summary of the goal of the experiment and how that goal was achieved in the experiment.
H. Post-lab questions or Editorial comment
• What did you learn in this experiment? What skills in lab practice did you develop through this expt?
This portion (Calculation and Discussion) is turned in at the beginning of class of the due-date
Overall Presentation (of lab notebook)
• Lab technique during experiment; example are, class preparation, safety glasses precautions and leaving
the laboratory clean.
• Report presentation: examples are the headings of each report that includes name, title, lab partner,
date and section #, witness signature.
• Legibility of report. Is the report easy to read or is important information jotted down by small print in
the corners of the lab report. The overall impression is important.
Lab Technique
• Safety: wear goggles, handle chemicals with caution, proper handling of lab equipment
• Leave lab clean and tidy
Score
15%
15%
10%
20%
20%
10%
10%
Unknown __________% Error
Score ______/10
________mass Zinc solution
______% m:v Zinc solution
Unknown __________% Error
Score ______/10
________ mass Zinc supplement
______% m:m Zinc supplement
Total (This total may be adjusted depending on lab technique and student conduct in the experiment)
50