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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: defencegrid on January 16, 2017, 01:32:35 AM

Title: Iodine Solution
Post by: defencegrid on January 16, 2017, 01:32:35 AM
I have a prac that says prepare 20ml of a 0.005M Iodine solution in Potassium Iodine. 
In brackets it tells you how to make a 1M solution of Iodine solution in Potassium Iodine.

it says:

"20ml 0.005M iodine solution (Dissolve 2.0g KI in 40ml water, add 1.25g of l2 and make up to 1L"

What I don't get, is that the molar mass of I2 is 126.90447 .  so 1.25/126.90447 = 0.0098M

So that molarity of that solution is about 0.0098, when we need a 0.005M solution?





Title: Re: Iodine Solution
Post by: mjc123 on January 16, 2017, 04:52:31 AM
126.9 is the molar mass of I, not I2.
Title: Re: Iodine Solution
Post by: defencegrid on January 16, 2017, 08:25:22 PM
Quote from: mjc123 on January 16, 2017, 04:52:31 AM
126.9 is the molar mass of I, not I2.

Oh yeah....Great, thank you.