Acid/Base Weight Change: Melting Point Increase?

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Discussion Overview

The discussion revolves around the weight changes of acid and base samples over time, particularly whether acids lose weight and bases gain weight, and the implications of these changes on melting points. Participants explore the underlying reasons for these phenomena, including intermolecular forces and absorption of moisture.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether an acid sample loses weight and a base sample gains weight over time, suggesting a relationship between weight gain and melting point increase due to intermolecular forces.
  • Another participant introduces the concept of equilibrium and mentions that an isolated system should neither lose nor gain weight, referencing Lavoisier's principle.
  • Concerns are raised about the water absorption capacity of bases and the potential evaporation of acids like HCl, which could explain weight changes.
  • There is speculation that weight gain could be due to absorption of water or carbon dioxide, which may influence melting points.
  • Participants discuss the concept of molality, with some providing definitions and clarifications, while others correct misunderstandings about its calculation.
  • One participant emphasizes the need for more information about the specific compounds and storage conditions to better understand the weight changes.

Areas of Agreement / Disagreement

Participants express a variety of views on the weight changes of acid and base samples, with no consensus reached on the reasons behind these changes or their implications on melting points. There is also disagreement regarding the definition and calculation of molality.

Contextual Notes

The discussion lacks specific details about the compounds in question and the conditions under which they are stored, which may affect the interpretations of weight changes and melting points. There are also unresolved mathematical definitions related to molality.

Who May Find This Useful

This discussion may be of interest to those studying chemistry, particularly in areas related to acid-base reactions, physical chemistry, and solution properties.

nemzy
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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
 
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very strange - never heard of this
 
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.
 
nemzy said:
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

I'd suspect the sample is either evaporating or absorbing moisture from the air.
 
when a sample gains weight, the melthing point rises
ARE you saying When Molecular mass increases(similar 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.
 
what is molality
 
Weight gain? Sure, picking up water --- and, carbon dioxide. The second item is the melting point booster.
 
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.
 
Molality:no of moles of solute /kg of solution.
 
  • #10
poolwin2001 said:
Molality:no of moles of solute /kg of solution.
Nope, it's moles solute/kg solvent. See: http://www.chemistry-dictionary.com/Molality
 
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