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Which process is used to test whether a solution containing a salt is saturated? A) add...

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mahmuda092569 | Student | eNoter

Posted September 30, 2010 at 2:23 AM via web

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Which process is used to test whether a solution containing a salt is saturated? A) add a crystal of the same salt to the solution, B) cool the ...

solution rapidly to see if crystals will be formed,C) heat the solution until it boils, D) stir the solution vigorously?

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william1941 | College Teacher | Valedictorian

Posted September 30, 2010 at 4:13 AM (Answer #1)

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If a solution containing a salt is saturated, no more salt can be dissolved in the solvent. In such a solution if more of the salt is added it cannot dissolve and instead settles at the bottom of the container as a solid.

Therefore to test whether a solution containing a salt is saturated, we can add a crystal of the same salt to the solution. If the solution is saturated the crystal that is added will not be dissolved as the solvent cannot accommodate any more of the solute and instead we can see the crystal at the bottom of the beaker.

 

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ndnordic | High School Teacher | (Level 2) Associate Educator

Posted September 30, 2010 at 7:06 AM (Answer #2)

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A saturated solution means that at that specific temperature you cannot dissolve more of the solute into the solvent.  In your case, if the solution is saturated then adding a crystal of the same salt, and stirring, would give you the best chance of determining of the solution is saturated or not.  It is important not only to add the crystal but also stir because some salts dissolve slowly.  If you just add the crystal and see it sink to the bottom that may indicate the solution is saturated or it may mean it takes time for the salt to dissolve.

Cooling the solution does not prove that the original solution was saturated.  If it was saturated, cooling it may result in a supersaturated solution rather than crystallization of some of the solute.  And if some salt does crystallize that would be expected even if the original solution was not saturated since most salts are less soluble at lower temperatures.

Heating would prove nothing and stirring vigorously would be pointless if there is no solute undissolved.

 

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trophyhunter1 | College Teacher | (Level 3) Senior Educator

Posted September 30, 2010 at 7:54 AM (Answer #3)

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The process to test whether a solution containing a salt is saturated is quite easily carried out. Simply add a crystal of the same salt to that solution. If the solution is truly saturated, this means it can no longer hold any additional salt. The salt will sink to the bottom as a precipitate. This can be seen in daily life when a cup of iced tea cannot hold another spoonful of sugar and crystals can be seen on the bottom of the glass, not dissolved. Factors such as temperature of the solvent and the nature of the chemicals involved all affect when the saturation point is reached. When a chemical in the lab is being purified by recrystallization, the chemical is dissolved in heated solvent first. When the liquid cools, the excess solute crystallizes, forming a precipitate on the bottom of the beaker. This can then be collected.

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