[Cavalier]

Ok...  I took Chem classes, but that was quite a while ago.  I need some help understanding this statement....

"20% aqueous sodium hydroxide (NaOH)"

If I have dry crystal NaOH that I purchased from Home Depot, how do I turn that into 20% aqueous sodium hydroxide.  And in particular, how do I do this without dissolving my garage or kitchen.  Does the % mean by weight?  20 grams of NaOH for every 100 grams of water?

Thank you all in advance.

RC

[Borek]

20g of NaOH per 100g of SOLUTION, not water.

[bberti]

Assuming your 20% is weight on weight, just add 80 grams of water (80 mL at 20 degrees Celsius) to 20 grams of NaOH.
You'll have [(20g NaOH) /(20g NaOH+80g water) ]*100 ==> 20g NaOH every 100g of solution.

[darko]

Assuming your 20% is weight on weight, just add 80 grams of water (80 mL at 20 degrees Celsius) to 20 grams of NaOH.
You'll have [(20g NaOH) /(20g NaOH+80g water) ]*100 ==> 20g NaOH every 100g of solution.

if you atempt to add temperature in calculation (in this case is better not to), then is more precise 4^oC,

i think that is more imprtant to explain that it is egzothermic reaction

[vmelkon]

Assuming your 20% is weight on weight, just add 80 grams of water (80 mL at 20 degrees Celsius) to 20 grams of NaOH.
You'll have [(20g NaOH) /(20g NaOH+80g water) ]*100 ==> 20g NaOH every 100g of solution.

if you atempt to add temperature in calculation (in this case is better not to), then is more precise 4^oC,

i think that is more imprtant to explain that it is egzothermic reaction

egzothermic or egg-zothermic. Nah, exothermic.

[darko]

Assuming your 20% is weight on weight, just add 80 grams of water (80 mL at 20 degrees Celsius) to 20 grams of NaOH.
You'll have [(20g NaOH) /(20g NaOH+80g water) ]*100 ==> 20g NaOH every 100g of solution.

if you atempt to add temperature in calculation (in this case is better not to), then is more precise 4^oC,

i think that is more imprtant to explain that it is egzothermic reaction

egzothermic or egg-zothermic. Nah, exothermic.

 

[Lord Ferrum]

That's why it's easier to use moles per liter 

[skbuncks]

That's why it's easier to use moles per liter 

Not if your doing it in your garage without access to a volumetric flask it isn't.

skb