[dedekagus]

1.i want to make NaOH 0,5 mol/L liquid from caustic soda (technical grade). How to measure it...?

2. How much the NaOH contain in casutic soda technical grade?
 

[Yggdrasil]

From the volume of solution that you need and the concentration of the solution you need, you can figure out the total number of moles of NaOH that you need in your solution.   The molecular weight of NaOH (39.9971 g/mol) tells you how much a mole weighs.  So, using the molecular weight, you can convert the number of moles to a mass, then weigh out that mass of NaOH, and use it to make your solution.

[dedekagus]

i know, but whate about the purity of Caustic soda, that we use

[Sam (NG)]

Technical grade is not a high grade of purity, but if that is what you are using to make the solution, then i assume you are in a situation that only requires lower standards of purity, meaning that the effect of the impurites on concentration when weighing out solid NaOH is minimal.  If you do need higher accuracy, you'll have to fork out the extra for better grade NaOH.

Chemical Grades