acids, bases, etc

nemzy

Suppose u let an acid sample sit for a week, does it lose weight after a period of time? and a base sample gain weight after a period of time? why is like this? and when a sample gains weight, the melthing point rises. is it because of the increased intermolecular forces? thanks

garytse86

very strange - never heard of this

chem_tr

Your logic is interesting. You should better consider equilibrium phenomenon; and Lavosier's very principle. An isolated system neither loses nor gains weight.

Your query reminds me of water absorption capacity of bases; as hydroxide ions are very powerful bases, hydrogen bonding may be excessive to absorb large quantities of water. Gaseous-originated mineral acids like HCl may lose weight as some of HCl evaporates away.

pack_rat2

I'd suspect the sample is either evaporating or absorbing moisture from the air.

poolwin2001

ARE you saying When Molecular mass increases(similiar compounds)melting point rises?
{ethane,ethane,propane }

In case of absorption/evaporation of water,there is a change in Freezing point/Boiling point in non ideal solutions which is proportional to molality.

garytse86

what is molality

Bystander

Weight gain? Sure, picking up water --- and, carbon dioxide. The second item is the melting point booster.

pack_rat2

This is a lot of speculation about a "sample" we know very little about. Questions: What compound is it? Under what conditions have it been stored? Any further info would help. As for the question about molality, it's moles of solute per kg of solvent, of a solution.

poolwin2001

Molality:no of moles of solute /kg of solution.

pack_rat2

Nope, it's moles solute/kg solvent. See: http://www.chemistry-dictionary.com/Molality