Chemistry Assignment Flashcards
Title:
Investigating the mass of vitamin C per tablet, using 3 different brand
Aim:
To calculate 3 different brands vitamin C tablet mass per tablet in comparison to a source
Underlying chemistry order of topics:
*Vitamin C chemical name and what it reacts with
*Redox equation
*What is a redox equation
*The ion-electron equations for the same redox
-Reduction: iodine acting as an oxidising agent, then what is an oxidising agent
-Oxidation equation
*Same redox written in full structural formula (With arrows to the hydroxyl and carboxyl functional groups)
*From the structures we observe when vitamin C oxidises, electrons are lost but also so is hydrogen
-Draw oxygen hydrogen ratio
*vitamin C is an antioxidant and why it is useful in food items
*in this experiment having the volume and concentration of iodine solution we can calculate the mass of vitamin C that was dissolved in our solution. Showing how much is present in a tablet
(Draw all apparatus with labels)
*Description of how experiment was carried out
-e.g all apparatus was rinsed thoughouly with the chemical that it would carry. And further describing the rest of the titration
Method:
I titrated the vitamin C solution with iodine and recorded the volume used, we did this for 3 different tablet brands and changed tablet once we had two concordant
Safety sentence:
I wore gloves in prevention of contact with iodine solution as it stains skin
Example Calculation: (average volume I2=26.15 and concentration I2=0.016moll-1) remember to convert cm³ into litres ÷1000§
4 sig fig=1.841x10³mg
Raw data with averages
Same as sheet
Averages:
29.4
32.55
26.15
Graph starting value:
Start with scribble and value is 1600
Analysis
Tesco % decrease=51.7%
ASDA % decrease=56.4
Morrisons % decrease=45.7
By comparing my calculated mass to the internet mass it is evident the calculations are higher from myself than the internet source. While there are a number of potential reasons my results are higher, from this table it show each result is higher by at least 841mg and upward
Conclusion:
In conclusion I have calculated the different masses of 3 vitamin C tablet brands and found that by comparing my results with the brand website values my results are greater than the source
Evaluation internet source:
The comparison data of my internet source is reliable due to it being sourced from a supermarket website is must meet EU regulation standards and their data will have been carried out in very reliable laboratory’s
Evaluation Vitamin C impurities:
Compared to the internet source my results were much higher, a reason for this could be impurities in the vitamin C sample. This could have interfered with my titration leading to inaccurate results. To prevent this I could use a pure vitamin C standard for calibration
Evaluation volatility of iodine:
Another reason for my higher than expected results could be iodine volatility leading to a loss of iodine from the solution thus the calculation of concentration of vitamin C would be inaccurate. To minimise iodine, loss the titration should be carried out quickly and in a closed environment.
Evaluation Improvement of experiment using potentiometric titration
To improve the experiment I could have used a different titration method such as a potentiometric titration to determine the end point more accurately. Also the end point may have been difficult to detect due to a gradual colour change, leading to over titration and inaccurate results. To improve the accuracy a colorimeter could be used
Evaluation Air oxidation of vitamin C
Lastly the air oxidation of vitamin C could have affected the concentration of vitamin C in the solution leading to inaccurate results. To minimise oxidation the vitamin C solution should be prepared fresh and protected from light and air.
