[Fragment_Error]

Ok, I need to find out the initial concentration of a reaction after mixing.

It is KI -> Na₂S₂O₃

The molarity of KI is 0.2 and the Volume was 20cm³

Now in my question it has:

For [KI]_ln

M_KI x V_KI = [KI]_ln x 50cm³

Which would mean:

0.2 x 20 = 4 x 50

= 200M

Which can't be right.

I know I'm missing something here, and just need a little help.

[Borek]

Which can't be right.

That's the only thing we agree.

Please explain what's the question/experiment and start with properly written and balanced chemical reaction. Then someone can be of some help.

[AWK]

Product

0.2 x 20 = 4 x 50

= 200M

is in milimoles
(for moles you should use volumes of solution  in liters)