Chemical Engineering - Stoichiometry - Discussion


The evaporation of aqueous solution of sugar causes its molarity to

[A]. decrease. (b) increase.
[B]. remain unchanged.
[C]. either (a) or (b); depends on the concentration of the solution.

Answer: Option B


No answer description available for this question.

Sandip said: (May 22, 2012)  
Molarity should increase because due to evaporation the concentration of sugar increases in water which hence increases its molarity.

Vikas said: (Aug 3, 2012)  
Molarity must increase because solute sugar is not evaporated in this evaporation process and volume of the solvent is decreasing that's why molarity must increases.

Clint said: (Oct 29, 2013)  
There must be an error with the choices itself. Answer is B but due to some reasons, the letter seem to be moved and adjusted.

Somdev said: (Sep 12, 2014)  
I agree with other comments. Molarity must increase.

Auchithya said: (Feb 17, 2016)  
Molarity = Number of moles of solute/volume of solution.

Due to evaporation, solute crystals lessen. So volume of solution also reduces. So, no of moles of solute and volume of solution both reduces hence Molarity remains unchanged because molarity pertains to no of moles of solute to particular vol of solution.

Realistic said: (Jul 2, 2016)  
Dear & Respected Auchithya.

Will you please explain your point in detail. I will be thankful to you.

Diksha said: (Sep 8, 2016)  
Crystals are not lesser because by dissolved and liquid is evaporated crystal remains same.

Tarak said: (Aug 20, 2017)  
Molarity should increase.

Umar Shaik said: (Aug 7, 2019)  
In a solution we have both water and solute. In the evaporation process solute doesn't evaporate that means solvent will evaporate. So the total volume of the solution will decrease. When the solution volume decreases then molarity will increase.

Raphael RS said: (Jun 4, 2020)  
It's unchanged, because molarity is nothing but the number of moles of solute present in a solution, the solution contains both solute and solvent so when the solvent get evaporate the molarity of solvent get decreased but the molarity of solute remains constant but it's getting concentrate.

Sanjoy Karmakar said: (Nov 3, 2020)  
Molarity should be increase.

Jaane said: (Feb 6, 2021)  
Molarity increases.

KOLA BENARJI said: (May 12, 2021)  
Molarity=no. Of moles of solute/one liter of solution.

In evaporation, we increase the concentration of solute (sugar concentration) means we evaporate (decrease) the aqueous solution (water) then the denominator in molarity decreases therefore the molarity increase.

Pavi said: (Aug 13, 2022)  
Molarity increases.

TANMAY SHAH said: (Oct 25, 2022)  
Yes, the Molarity should be Increase.

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