If I mix, say, 5 moles of ethanoic anhydrate with 10cm of water, will the molarity be changed, or will there still be 5 moles of the ethanoic anhydrate?

chickenpoo2

I'm guessing that if you add 10cm of water then you will still have 5 moles of ethanoic anhydrate, but it will just be diluted.because you aren't getting rid of any ethanoic anhydrate and you aren't adding any! Aug 16 05, 12:00 PM

Flynn_17

I thought that too. *sigh* My life depends on this Chemistry coursework. Results on Thursday! Wish me luck, guys. Aug 16 05, 12:53 PM

BillyWhiz

You are mixing your units. A mole is a weight but molarity is weight dissolved in a litre of solvent Aug 16 05, 1:25 PM

gmackematix

Pardon my ignorance here, but what is the formula of ethanoic anhydrate? I'm just thinking that "anhydrate" suggests that adding water to it will chemically change it into 5 moles of something else (like ethanoic acid?) and some of the water will be used up in the process. I agree with BillyWhiz though. A mole is about 6 x 10^23 particles, in this case, molecules, e.g a mole of water is 6 x 10^23 water molecules and will weigh 18g (adding the atomic masses of H+H+O). The number of moles of a substance is not to be confused with molarity which means the concentration in moles per litre of solvent. Aug 16 05, 3:59 PM

peasypod

Formula for acetic anhydride is (CH3CO)2O, if I recall correctly. Aug 16 05, 5:06 PM

peasypod

...AKA ethanoic anhydride... Aug 16 05, 5:08 PM

kevinatilusa

I'm not sure if you'd still have the same amount of Ethanoic anhydrate (anhydrite?) before and after adding the water. The trouble is the reaction (Ethanoic Anhydrate)+(Water)<=>Ethanoic Acid If we put a system together which has all the reactants on the left side but nothing on the right, it will tend to shift rightwards, that is some of the Anhydrate will combine with water to form Ethanoic Acid. This would mean there would be less anhydrate. Aug 19 05, 7:33 AM