Dilution directions

[Nunudada]

Hi,

Can anyone help me solve this calculation please, here it is :

Give dilution directions for 500ml quantities of a 1 in 5000 solution of Potassium permanganate from a 0.25% solution.


I have no idea from were to start. I have just started a course of pharmacy technicians and would like some help on how to work this calculation out.
I thank you in advance,

Regards,
Nunudada

[framesh1ft]

okay you are starting with a 1 in 400 soln. I reckon the rato is thus pot perm: water 1:12.5... if this is what they mean, they should really specify in ppm.

[Nunudada]

I dont think the question specified that. I was think of dividing 5000/0.25 but not sure if it is right

[framesh1ft]

Why would you do that?

continuing...you have a 0.25% soln = 1 in 400. To make 500 mL of a 1 in 5000 soln.

500/12.5=40 ml of the 0.25% KMnO4
500-40=460 ml of water.

And if you were keeping a notebook it would be something like this...
Preparation of a 200 ppm solution of KMnO4: To a 500 mL volumetric flask was added 40 mLs of 0.25% KMnO4 and dH20 to 500 mL.