how do you create a 0.2N solution of sodium hydroxide using powdered sodium hydroxide

[silicaphysics]

All the comments above are relevant, but I would stress that IF the NaOH is powdered, it will he highly contaminated with carbonate. Even pellets are highly contaminated (age and exposure dependent). In analytical chemistry, we prepare a saturated solution of NaOH and allow the carbonate to precipitate. One can prepare standard dilutions of NaOH from this stock supernatant.

[mirving]

Sodium hydroxide solutions are notoriously suspect for reason others have pointed out, they also react with CO2 if left exposed to air and will slowly react with glassware. Traditionally the concentration of a NaOH solution is measure by titration using a primary standard such as KHP. One way to determine an accurate concentration of a NaOH solution is by titration against a known HCl solution using calibrated glassware and phenophalien as an indicator. The exact concentration of an HCl solution can be determined by titrating a solution containing a known mass of dry potassium hydrogen phthalate (KHP) with phenophalien as indicator. A calibrated pH meter can be used as a replacement for the indicator. You can also purchase known HCl solutions to simplify the procedure a little.

[wtwinter]

I am surprised at the absence of one important comment on the prep of 0.2N NaOH. Molarity and  normality are both defined in terms of a quantity (moles or equivalents) of a chemical  per liter of solution ( not solvent).  If you add 8 grams of, theoretically, absolutely pure NAOH to exactly 1 liter of water your solution will be approximately 0.2N but not exactly the volume of the solution will not be exactly one liter.  That is why it is common to make an approximate solution,using say 990 ml of water,fully dissolve the solute in that water and then top of and mixin additional water until a volume of 1.000 liter is obtained. Depending on the accuracy requirements for your process this may be unnecessary.

Secondly, water also dissolves CO2, as  indicated by pH values for distilled water stored in a lab typically being less than 6.0.