Science Buddies: "Ask an Expert"

To Whom this may Concern,

I am currently working on the Science Project :Do Oranges Lose or Gain Vitamin c After being Picked?
I am having a hard time understanding the instructions on how to calculate the Vitamin C samples for
this project. Could i Please get detail instructions on how to calculate. Am I suppose to calculate each
sample or am i suppose to calculate them all together. Am i suppose to average the orange sample only
or the Vitamin C Sample also. Please help my project is Due Feburary 21,2012. All of my sampling is complete.
The calculations have me at a standstill. My parents are also very confused about the instructions.

Thank You
Alex [last name removed by moderator]
6th Grade
[e-mail address removed by moderator]



n

Hi Alex! Welcome to science buddies. Just to let you know, you should not be posting personal information, such as your email address, on the forums.

You're talking about this project, right?
https://www.sciencebuddies.org/science- ... p043.shtml

The site does explain how to do the calculations, but I can see how it comes off as confusing. I'm going to try my best to explain it clearly, and if you don't understand, please tell me so I can help you more.

To do the calculations, you should set up a proportion using the amount of iodine solution you needed to titrate both the orange juice sample and the vitamin C solution that you made.
We'll use the examples they used on the webpage. The results were 8.5 mL of iodine for the vitamin C solution and 6.8 mL for the orange juice.
Since you prepared the vitamin C solution as 1 mg/mL, there is 20mg of vitamin C in your 20mL solution.
So, to find the amount of vitamin c in the orange juice, you would set up a proportion that looks like this:

(6.8 mg/mL of iodine)/ (X grams of vitamin C in orange juice) = (8.5mL of iodine)/ (20 mg of vitamin C from the tablets)

We set this up as a ratio, because we know that 6.8 divided by the amount of vitamin C in orange juice will be the same as 8.5 divided by the amount of vitamin C from the tablets.

To solve this problem, You can multiply 6.8 mg/mL by 20mg and 8.5 mL by your unknown value (x).
Then, the equation should look like this:

6.8*20=8.5x
when you multiply further, you will get:
136=8.5x
and when you divide both sides by 8.5, you will get:
x = 16 (mg of vitamin C from orange juice)

For this experiment, I would average the amount of iodine it took to titrate the vitamin C and the amount of iodine it took to titrate the orange juice before adding them into the equation.

Did this help? If not, I will be here to help. Ask any questions you need.