What is meant when someone says 50% solution of NaCl?

[mikepl1]

when someone talks about a 50% NaCl solution or a 35% ethylene glycol solution, what does this really mean? Is this the percentage of the solute in the solution by mass, moles, or what?
Thanks.

 

[gravenewworld]

when someone talks about a 50% NaCl solution or a 35% ethylene glycol solution, what does this really mean? Is this the percentage of the solute in the solution by mass, moles, or what?
Thanks.

Depends if you see v/v (volume/volume) or w/v (weight/volume) %. 50% (w/v) NaCl would be 50 grams in 100 mL of water. 35% ethylene glycol would be 35 mL ethylene glycol + 65 mL water = 100 mL solution, but 35% of that solution is ethylene glycol.

In reality volumes don't add, but 99% of the time for lab purposes it doesn't matter if you're off by 0.01 mL.

 

[chemisttree]

Depends if you see v/v (volume/volume) or w/v (weight/volume) %. 50% (w/v) NaCl would be 50 grams in 100 mL of water.

I always interpreted that to be 50 grams of NaCl in 100 mL of solution (solution = water + salt).