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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: biskit on January 16, 2007, 10:57:37 AM

Title: About concentration of sodium hydroxide
Post by: biskit on January 16, 2007, 10:57:37 AM

Hi Guys,

I'm stuck at an experiment that i had to use 3M NaOH/ethanol. The problem is, i only had 5M of NaOH with me now and i'm a bit confused by the term "NaOH/ethanol". If it is 3M NaOH without the "/ethanol" i could have easily use De-ionised water to dilute the 5M to 3M but i'm rather confused abt the 'ethanol' part.

My question is; does the 'ethanol' mean that i need to use ethanol to dilute the 5M NaOH instead of using de-ionised water?

Another qn: Do all ethanol come in 1M concentration? i've some purchased from fluka biochemical but it only states 'absolute' ethanol and doesn't mention anything abt Molar concentration. Also , does the word 'absolute' mean 100% ethanol?

Would appreciate if anyone can help enlighten me a bit. Thanks in advance!

Title: Re: About concentration of sodium hydroxide
Post by: Yggdrasil on January 16, 2007, 01:38:01 PM

3M NaOH/ethanol means making a solution of 3M NaOH with ethanol as the solvent, not water.  So, you cannot use your 5M stock of aqueous NaOH to make the 3M ethanolic NaOH.

Yes, absolute ethanol means 100% ethanol (200 proof).  You wouldn't associate a concentration with absolute ethanol because its not a solution.  In the same way, you don't normally say that pure water is a ~55M solution of H₂O.