Colligative properties

[joonkimdds]

Dissolved solutes alter some physical (colligative) properties of the solvent water because they change the:

a) concentration of the water.
b) hydrogen bonding of the water.
c) ionic bonding of the water.
d) pH of the water.
e) temperature of the water.

I don't know the answer 🙁

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[AndyK]

I think it's A...

 

[aquafreshlovin]

could you please describe why you think it's A?

not getting it either

 

[Svart Aske]

By definition, colligative properties result from dilution of the solvent ("colligative" means depending on number of particles, not nature of particles), hence A. The rest of the choices are too vague or not necessarily true.

 

[Isradoc1983]

I would say its A as well, because the H bondings b/w water molecules will stay the same and the rest doesn't make much sense

 

[IWantSmile]

Dissolved solutes alter some physical (colligative) properties of the solvent water because they change the:

a) concentration of the water.
b) hydrogen bonding of the water.
c) ionic bonding of the water.
d) pH of the water.
e) temperature of the water.

I don't know the answer 🙁

When I read this question, in my mind the "dissolved solute alter some physical properties of the solvent water" and why is it. I thought the question asked me about change in solution properties.

For example, when NaCl is place in water, those ions that less tightly held because of their position at a corner are exposed to water molecules, which collide with them until an ion happens to break free.
More water molecules then cluster around the ion, stabilizing it by means of ion-dipole attractions. This process continue until the entire NaCl has dissolved. (--- "Dissolved solutes alter some physical (colligative) properties of the solvent water" and why.)

Therefore, answer is C.

 

[joonkimdds]

Therefore, answer is C.

I think that makes sense too!

 

[dl9006]

i think it's hydrogen bonding between water
and the colligative property the question is referring to is vapor pressure

can't be ionic bonding between water since water can't have ionic bonds

and the question never mentioned anything about NaCl

the solute dissolved could be uncharged molecules like glucose

 

[doc3232]

How can water ever have ionic bonding?
I mean NaOH filly dissociates in water and hence won't exist.
IMO, there won't be ionic bonding.

When I read this question, in my mind the "dissolved solute alter some physical properties of the solvent water" and why is it. I thought the question asked me about change in solution properties.

For example, when NaCl is place in water, those ions that less tightly held because of their position at a corner are exposed to water molecules, which collide with them until an ion happens to break free.
More water molecules then cluster around the ion, stabilizing it by means of ion-dipole attractions. This process continue until the entire NaCl has dissolved. (--- "Dissolved solutes alter some physical (colligative) properties of the solvent water" and why.)

Therefore, answer is C.

 

[joonkimdds]

Hey guys~ I just read a sentence about a colligative properties and hope this is the key to solve this problem

"Effect of solute independent of chemical properties"

H-bond, ionic bond, pH, temp... aren't they all chemical properties?
oh wait, are bonds physical :?

 

[IWantSmile]

How can water ever have ionic bonding?
I mean NaOH filly dissociates in water and hence won't exist.
IMO, there won't be ionic bonding.

This question is about the concept of the " Solutions and their properties". Which I think ( may be not, since I do not know the real answer; but I can immediately identify what they are asking.)

The example that I gave was NaCl but it is true that nonpolar organic substances like cholesterol, C27H46O, dissolve in nonpolar organic solvents like benzene because of the the similar London dispersion forces present among both kinds of molecules. Oil, however, does not dissolve in water
because the two liquids have different kinds of intermolecular forces.
Therefore, like all chemical and physical processes, the dissolution of a solute in a solvent has associated with it a delta G.

and actually when you said, " I mean NaOH filly dissociates in water " also saying samething. Solvent-solvent (NaOH and H2O are solvent-solvent form of solution. NaCl and H2O are solute-solvent. ( just for the example, when you need to neutralize the NaOH but you do not have any strong acid around then mix with tons of water. water will eventually rip a part of NaOH and neutralize.)

The question was about what happen when the solute dissolve in solvent in chemical and physical properties.

 

[IWantSmile]

Hey guys~ I just read a sentence about a colligative properties and hope this is the key to solve this problem

"Effect of solute independent of chemical properties"

H-bond, ionic bond, pH, temp... aren't they all chemical properties?
oh wait, are bonds physical :?

you are right about chemical bonds.

A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules; and they are the forces of attraction that hold atoms or ions together to form molecules.
Different types of chemical bonds which you already mentioned. and their varying intensity are directly responsible for some of the physical properties are such as hardness, melting and boiling points, solubility, and conductivity. Hope this help.

 

[joonkimdds]

but then wouldn't A be the correct answer becuz A is the only physical property and the rest of choices are chemical properties? (If it's true that colligative properties are only depending on physical properties).

 

[bigstix808]

the answer is "hydrogen bonding" (B i think)....anyway...if you throw in some salt into some water, what happens to the boiling point? it goes up right. is this because you messed with the ionic bonds of water??? (laughing to my self --- water does not ionic bond!!) NO, it is because you lowered the vaper pressure, which is a direct result of disrupting the H bonding between the water molecules.

how can adding a solute to a solvent change the concentration of the solvent???

come on guys, i know you learned this in gen chem...stop over analyzing the questions!!

 

[anesthesia_209]

the answer is "hydrogen bonding" (B i think)....anyway...if you throw in some salt into some water, what happens to the boiling point? it goes up right. is this because you messed with the ionic bonds of water??? (laughing to my self --- water does not ionic bond!!) NO, it is because you lowered the vaper pressure, which is a direct result of disrupting the H bonding between the water molecules.

how can adding a solute to a solvent change the concentration of the solvent???

come on guys, i know you learned this in gen chem...stop over analyzing the questions!!

I'm gonna have to disagree with this and also go with A.
If you look at it from a partial pressure standpoint. The partial pressure (therefore, boiling point and vapor pressure) is dependent on the concentration.
With your logic, bigger molecules would have a greater effect on disrupting the H bonding between water molecules, which is not the case seeing as only the number of particles matter in regards to colligative properties. This would also cancel out disruption of ionic bonding.
Since the identity of the solute doesn't matter, pH (acidic/basic solute) nor temperature (if dissolution is endothermic or exothermic) would matter neither.

 

[xhamburgersamx]

This question looks really familiar...i'm not going to point fingers but where did you get this question from

 

[dl9006]

now that I think about it again, I will have to say A/concentration of water.


Reason being, I was thinking of the usual way to calculate concentration (ie mol of solute/L of solvents) but the concentration this question is using is Mole Fraction (mol of A/ sum of mol A+B) so water does have a concentration and mole fraction.

Thus you use this mole fraction of water in Raoult's law to find the vapor pressure.


btw where is this question from?