[defencegrid]

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?

[mjc123]

126.9 is the molar mass of I, not I₂.

[defencegrid]

126.9 is the molar mass of I, not I₂.

Oh yeah....Great, thank you.