Most basic solution when dissolve in water?

[Awuah29]

Which gives the most basic solution when dissolve in water?

A. H3PO4
B. NaH2PO4
C. P2O5
D. NaNO3
E P2O5Na3PO4

Anyone knows the anwer to this problem ? I think its A

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[llopop]

My answer is D. Your looking for the most basic solution therefore the solution would have the highest concentration of [OH]-. NaNO3 would produce the -NO3 ion which would produce the most basic solution in h20.

 

[dddsmack]

Break everything down by looking at their conjugates.

Strong acids conjugate weak bases and weak acids conjugate stronger bases.
So to get the stongest base, look for the conjugate of the weakest acid.

 

[Awuah29]

My answer is D. Your looking for the most basic solution therefore the solution would have the highest concentration of [OH]-. NaNO3 would produce the -NO3 ion which would produce the most basic solution in h20.

sorry, my friend
the answer is E! Still don't get it. Anyone have a suggestion or way to figure this out. Ionizing in water and look for the base?

 

[llopop]

Everything DDSmack says is true but dissolving a weak acid will still produce a lower PH solution then dissolving any base. I wasn't reading carefully and didn't notice that the answer E is correct because the phosphate ion (-3PO4) is more basic then nitrate (-NO3). The first step is to firgure out which compounds are bases and which are acids. Since we are looking for the most basic condition the acids can be disregarded and the next step is to look which ion is more basic (ie which ion would be more likely to abstract H+ from H20). Let me know if there is other ideas about this problem

 

[andyjl]

Everything DDSmack says is true but dissolving a weak acid will still produce a lower PH solution then dissolving any base. I wasn't reading carefully and didn't notice that the answer E is correct because the phosphate ion (-3PO4) is more basic then nitrate (-NO3). The first step is to firgure out which compounds are bases and which are acids. Since we are looking for the most basic condition the acids can be disregarded and the next step is to look which ion is more basic (ie which ion would be more likely to abstract H+ from H20). Let me know if there is other ideas about this problem

how do u figure that phosphate ion (PO4 3-) is more basic. IS it because it has four oxygen atoms which gives the ion a more attractive pull for H+ as opposed to the NO3- ion?

 

[Awuah29]

how do u figure that phosphate ion (PO4 3-) is more basic. IS it because it has four oxygen atoms which gives the ion a more attractive pull for H+ as opposed to the NO3- ion?

yaeh, would like to know that one too

 

[doc toothache]

how do u figure that phosphate ion (PO4 3-) is more basic. IS it because it has four oxygen atoms which gives the ion a more attractive pull for H+ as opposed to the NO3- ion?

The salt from a strong base and a strong acid, will give neutral salts. NaNO3)

Na3PO4 is a product from a strong base and a weak acid; the salts are basic.

 

[llopop]

how do u figure that phosphate ion (PO4 3-) is more basic. IS it because it has four oxygen atoms which gives the ion a more attractive pull for H+ as opposed to the NO3- ion?

To determine the strengths of the ions we must look at the corresponding acids, in this case H2PO4 (H3PO4 that has already lost a H+) and HNO3. HNO3 is a relatively strong acid which will produce a relatively weak base in the case of NO3-. H2PO4 is a very strong acid and will produce a weak base in the case of HPO4-. However, this species is also an acid but the second H+ is must less acidic. Therefore being a weak acid it will dissociate into a strong base, PO4-3, which would better pull H+ away from a water making this ion in solution the most basic.

 

[mhamilton23]

Therefore being a weak acid it will dissociate into a strong base, PO4-3, which would better pull H+ away from a water making this ion in solution the most basic.

you may want to re-word your explanation. It seems to imply that H2PO4 - is the answer. Only a small amount of HPO4 2- will dissociate into PO43- due to its small dissociation constant, and the dominant form in solution will remain HPO4 2-. Any PO43- that does form will react as a strong base and return to HPO4 2-, negating any significant net change in pH. It is in fact the Na3PO4 that will dissociate into PO4-, react with water and become HPO4. This will lead to a net change in pH as the extraction of H+ from water yields an equimolar amount of OH- as a byproduct.

It seems like you knew what you were doing, but I just thought your explanation should be clarified. Take care.

 

[llopop]

you may want to re-word your explanation. It seems to imply that H2PO4 - is the answer. Only a small amount of HPO4 2- will dissociate into PO43- due to its small dissociation constant, and the dominant form in solution will remain HPO4 2-. Any PO43- that does form will react as a strong base and return to HPO4 2-, negating any significant net change in pH. It is in fact the Na3PO4 that will dissociate into PO4-, react with water and become HPO4. This will lead to a net change in pH as the extraction of H+ from water yields an equimolar amount of OH- as a byproduct.

It seems like you knew what you were doing, but I just thought your explanation should be clarified. Take care.

I like your clarification, thank you. I was trying to answer the question about determining relative ion strengths, not actually describing the nature of the soultion. But I can see how my wording may be confusing