|Determination of vitamin C content||Honors Chemistry|
background [prelab assignment (25 points) due at the beginning of lab; put a copy in your lab NB]
what is a calibration (or standard) curve ?
basis of a least-squares regression analysis
describe the syntax / protocol in using MS Excel to generate the calibration curve. as appropriate, include sketches / screen shots to clarify your response and use in-text citation.
sketch a data table (i.e. not calculations) for your experimental measurements (i.e. review the purpose & content of your lab report)
msds on I2 (aq)
determine / compare the concentration of vitamin C in various samples based on the following reactions
starch (colorless) + I2 --> starch - I2 complex (color)
and using a calibration / standard curve.
fulfill various aspects of the NGSS science & engineering standards.
microwell plates; micropipets
aqueous solution of starch, I2 (0.2 g I2 + 0.17 g KI / 200 mL), various [known] of vitamin C, and various fruits / juices
mix 200 µL of a vitamin C solution & 5 drops of the starch solution in a well of a microplate
add and count # drops of the I2 (aq) solution until there is a permenant color change in the solution; record its value
Content of lab report [40 points]
basis of least-squares analysis; illustrate using Excel simulation
results (10 points)
calibration / standard curve; include the equation & R2 value for the curve
determination of vitamin C content in your sample; show your work
discussion [20 points]
statistical data analysis: comparison of vitamin C content in various samples, include interpretation of p-value
vitamin C is an antioxidant; what is an antioxidant ?
what are the biological effects of oxidizing agents ?
based upon the preceding questions, what is a potential biological effect of vitamin C ?
describe / list two NGSS science & engineering practices that correlates to an aspect of this laboratory activity; provide an example in the lab & this lab report that meets these practices
MS Excel tutorial to curve-fit (i.e. regression analysis; may need to "add-in" analysis tool kit)
lab activity source (examples): site 1 & site 2 [access 4 / 2009]