Vitamin C Lab

On Monday and Tuesday, we performed the Vitamin C lab. My pre lab question was a math one, and it really wasn't hard at all. You just needed to know the formula of calculating concentration by dividing the drops of iodine needed to reach the endpoint of the sample over the drops of iodine needed to reach the endpoint of the standard. The actual lab consisted of measuring the number of drops of iodine were needed to reach the endpoint (when the solution turned permanently blue) of various fruit juices: pear, apple, grapefruit, v8. We then compared these numbers to the number of drops needed to reach the endpoint of a standard Vitamin C solution, made by a dissolved 500mg Vitamin C tablet in 500mL of water. We performed 3 trials while everyone else mostly performed 2 trials. This was to make sure we were being extra accurate, but when we actually looked back at our data for the trials, it seemed as if that extra trial just threw the average off. For example, the standard solution had endpoints of 39, then 27, and finally in the 3rd trial, it had an endpoint of 55. So, it totally threw off the average of the endpoint of the solution. This was probably due to the fact that we did the third trial on the second day of lab, when we had a new standard made. The standard was most likely much different than the standard from day one, throwing our number off.

Making the standard: mini tornado!

Clear solution of  juice

Some iodine has been added and the solution turns blue for a second
before disappearing back to clear

Endpoint has been reached!

Finally, we compared the numbers to figure out which juice had the highest concentration. The more drops of endpoint, the higher the concentration that solution would have. The lineup from most concentrated to least was Vitamin C standard, apple juice, v8 Golden Goodness, and finally, pear nectar.

Overall, this lab was pretty interesting to watch the color of solutions change. It did grow tedious for the solutions (Vitamin C standard) that took a large number of drops for it to turn blue. I enjoyed this lab and look forward to the future labs of this unit.