procedure for a report

Grading Guidelines

Investigation 20: How Much Cobalt Is in the Soil?

General

 Report is due by next week on:_______. Late lab reports will not be accepted.

 One copy of the report per group (hard copy or e-copy sent by email).

 Attach the contribution sheets to the end of the report.

Formatting (points can be deducted if these items are not followed)

 Title page with Investigation name, date, lab section, group members’ names, TA’s name.

 Must be written in third person, past tense, passive voice; no use of first person, and no contractions or

slang. Uniform in spacing (double space) and fonts,

 Label each of the sections listed below, bold or underlined.

 Use proper grammar and spelling. Use superscripts and subscripts for chemical formulas and scientific notation. Remember to put a zero in front of the decimal point.

 Include all bibliographic entries of all reference material used.

Introduction (l.5pt)  Briefly describe the goal in this investigation.  Briefly explain the spectroscopy technique used in the investigation.  Describe the following concepts and explain how they relate to this lab:

o The Beer-Lambert Law o Standard curve (absorbance vs. concentration)

Procedure (2.5pts)

 Provide a list of reagents/equipment made available in the lab that you used.

o Molarities of solutions must be listed correctly.

o Proper subscripts and physical states are very important.

 Provide a clear description (in a paragraph style) of the procedures used during the course of the

experiment; include concentration/volumes of solutions. This should be detailed enough that another

group could duplicate your work.

o Describe the analytical procedures followed. Include proper use of the spectrometer and the cuvette;

the calibration of the spectrometer, why and when....

o Be sure to describe how the data was gathered in the course of the experiment.

 When many solutions are made of varying volumes and concentrations, a table of just the values

used to make the standard solutions can be placed in this section instead of writing it all out in

paragraph form. Don’t include the absorbance values because they should be listed in Result. Results (4.5pts)

 What was the wavelength of maximum absorbance (λmax)?

 Figure: Calibration curve of absorbance vs. concentration of the standard solutions.

o Including best fit line, best fit line equation and R2 value.

o The graph should be properly labeled with a title and axis labels.

 Table: Organize the data in a table (numbered with a descriptive title) showing concentrations of cobalt (II)

standard solutions and the corresponding absorbances.

DUE: ____________

Due at the beginning of Lab.

Make sure you staple all

contribution sheets to the back of

the Lab Report

 Sample Calculations: For each calculation, clearly explain from where the values came and the purpose for

doing that calculation.

o ONE sample calculation of determining the needed volumes of cobalt (II) stock solution and distilled

water for making a 10-mL diluted solution (choose a final concentration from your experiment

notes).

o ONE sample calculation of plugging in Absorbance of the unknown sample to the Beer-Lambert

Law (the best fit line equation of your calibration curve) to get its concentration.

o ONE sample calculation of finding the amount (in the unit of milligrams) of cobalt in one kilogram

of soil. Look at your lab manual for the information on how the unknown cobalt solution was

prepared.

Discussion (3.5pts)

 Discuss how closely the calibration curve matches a straight line and how that might indicate how accurate it

is (Refer to the R2 value). Also look at the y intercept and what its value means.

 Discuss possible errors and limitations in the procedures used in this investigation.

 Refer to the information provided in your lab manual and discuss whether there is enough cobalt in the soil

sample tested in this lab. If not, determine how much cobalt (II) nitrate should be added to the soil to meet

the necessary nutritional needs of the animals. Include any necessary calculations here.

Conclusions (2pt)

 Summarize what results were determined (without restating actual results).

 Did the experiment succeed? i.e.: Were all of the objectives mentioned in the “Introduction” achieved?

 Elucidate on the utility of Beer-Lambert’s Law and include your recommendations to the cooperative

extension service regarding amending soil of the country farms.

Works Cited (1pt)

Reference the manual and other reputable sources using ACS format.