Determination of vitamin C content Honors Chemistry

background [prelab assignment (25 points) due at the beginning of lab]

1. what is a calibration (or standard) curve ?

2. basis of a least-squares regression analysis

3. describe the syntax / protocol in using MS Excel to generate a graph. as appropriate, include sketches / screen shots to clarify your response

4. sketch a data table (i.e. not calculations) for your experimental measurements (i.e. review the purpose & content of your lab report)

5. download / save *.swf file, then use Raffle to run simulation to analyze simulated data for the reaction involving KMnO4 to solve for the [Fe+2]

5. msds on I2 (aq)

purpose

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.

materials

microwell plates; micropipets

aqueous solution of starch

I2 (0.2 g I2 + 0.17 g KI / 200 mL)

various [known] of vitamin C (~ 1 mg vit C / mL), and various fruits / juices

methods

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

data analysis

student design

 

Content of lab report [40 points]

introduction

basis of least-squares analysis

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

questions

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

web resource

lab activity source (example):  site 1  [access 6 / 2022]

use in-text citation and bibliography as appropriate