Trick Question? (Making a solution)

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Discussion Overview

The discussion revolves around the feasibility of creating a 0.5 M KNO3 solution at 12 degrees Celsius, focusing on solubility, temperature effects, and calculations related to molarity and Ksp. The context is a solubility lab assignment.

Discussion Character

  • Homework-related
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant notes that temperature affects the ability to make solutions, suggesting that reactions slow down at lower temperatures.
  • Another participant confirms that a 0.5 M solution of KNO3 corresponds to 0.5 moles per 1 L of solution and questions the relationship between temperature and this calculation.
  • A participant asks for the solubility constant of KNO3 at 12 degrees Celsius, indicating uncertainty about its solubility at that temperature.
  • There are inquiries about calculating Ksp without known concentrations, with one participant suggesting that plugging in 0.5 for concentrations could yield a Ksp value.
  • Another participant mentions that KNO3 is a well-soluble salt and suggests checking reliable sources for its solubility in grams per 100 g of water.

Areas of Agreement / Disagreement

Participants express varying degrees of uncertainty regarding the solubility of KNO3 at the specified temperature and the implications for creating the solution. There is no consensus on whether a 0.5 M solution can be made at 12 degrees Celsius, and multiple viewpoints on the calculations and concepts involved are presented.

Contextual Notes

Participants reference the need for specific solubility data and the relationship between temperature and molarity, indicating that assumptions about solubility and reaction rates may not be fully resolved.

Who May Find This Useful

This discussion may be useful for students and educators involved in chemistry or related fields, particularly those interested in solubility, solution preparation, and the effects of temperature on chemical reactions.

needphyshelp
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Homework Statement


A student wishes to make a 0.5 M KNO3 solution at 12 degrees C. Is this possible? Explain, and show calculations to support your answer.
[This is a question related to a solubility lab]


Homework Equations


In my experiment, I saw that as temperature decreased and as volume increased, molarity decreased, but I don't know if temperature is actually related to this observation.


The Attempt at a Solution


.5 M solution = .5 moles KNO3/1L, right?
Does temperature affect this?
 
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Temperature effects any ability to make any kind of solution, mainly because reactions slow down with a decrease in temperature.

As for molarity, bond forming and other reactions take longer to occur because of the cold. You might want to look up the freezing point of KNO3 if possible.

And to answer your question, yes. a 0.5 M solution of KNO3 means 0.5 moles per 1 L soln.
 
needphyshelp said:

Homework Statement


A student wishes to make a 0.5 M KNO3 solution at 12 degrees C. Is this possible? Explain, and show calculations to support your answer.
[This is a question related to a solubility lab]


Homework Equations


In my experiment, I saw that as temperature decreased and as volume increased, molarity decreased, but I don't know if temperature is actually related to this observation.


The Attempt at a Solution


.5 M solution = .5 moles KNO3/1L, right?
Does temperature affect this?

What's the solubility constant of KNO3 AT 12 degrees C?
 
How can I calculate Ksp without having the concentrations? I know Ksp = [K+][NO3-]... would I just plug in .5 to get Ksp and go from there?
 
needphyshelp said:
How can I calculate Ksp without having the concentrations? I know Ksp = [K+][NO3-]... would I just plug in .5 to get Ksp and go from there?

I would think so; you have 0.5mol of KNO3 assuming 1L of solution, so that means you have 0.5mol [K+] and 0.5mol [NO3-]. This would give you a Ksp of 0.25, but then again it's been a while since I've done this.
 
This is pretty well soluble salt, so it will not have Kso listed. However, if you will check CRC handbook or some other, similar source, you should be able to find what is KNO3 solubility in grams per 100 g of water - check, if it is not less then 0.5M.
 
Thank you all so much for your input - I now have a few different ways to look at this problem. I really appreciate it!
 

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