Gen Chem questions

[raom_dtpi]

1) What happens to the solubility of Sodium Sulfate if put in a basic solution?

3) How do you determine if an aqueous solution of a salt is acidic or basic?
(Ex: Nacl, NH4 NO3)

Thanks!
Scout

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[bonez318ti]

1) What happens to the solubility of Sodium Sulfate if put in a basic solution?

3) How do you determine if an aqueous solution of a salt is acidic or basic?
(Ex: Nacl, NH4 NO3)

Thanks!
Scout

3) It depends on what disassociates from the salt. For example, NaCl will disassociate into Na and Cl. Cl- is the conjugate base of a strong acid, which means that if put into water, it isnt strong enough of a base to pull an H off of H2O.. so no H's are formed, meaning that there will be no change in pH. On the other hand, NH4 is the conjugate acid of a weak base (NH3), that means that it will diassociate to some degree, donating protons to the aqueous mixture, increasing the H concentration and thus decreasing pH. Not sure about NO3 though..

 

[chopper]

No3 is the conjugate base of a strong acid (HNO3). Same arguement as Cl- and Na+. No acid/base tendency in water. So in your example, NH4NO3, it will be slightly acidic (from the NH4). If you have conjugates of 2 weak acids/bases (e.g. NH4 CH3COO) - you need to look at the K values. The one with a higher K will dissociate more, hence more of an effect.

 

[sdnstud]

a salt consists of a cation and an anion.

if the cation is from Gp1 and Gp2...then the solution is neutral
if the cation is transition metal cation..then the solution is acidic

if the anion is a conjugate base of a strong acid...the solution is neutral
if the antion is a conjugate base of a weak acid..then solution is basic

NaCl...Na+ is a group 1 metal..therefore it's neutral...Cl- is a conjugate base of a strong acid..therefore it's neutral...NaCl is a neutral salt

Na2SO4....Na+ is a group 1 metal..therefore it's neutral....SO4 is a conjugate base of a weak acid (HSO4-)...therefore it's basic....sodium sulfate is a basic salt

 

[smc927]

ExamKrackers makes a note that when it comes to salts, cations act as weak Lewis acids in solution. This does not apply to alkali metals and alkaline earth metals.

ExamKrackers is awesome.

 

[anitra627]

1) So... can anyone answer " What happens to the solubility of Sodium Sulfate if put in a basic solution?"

Does the solubility of Na2SO4 decrease since Na2SO4 is a basic salt that's being added to a basic solution? Or does it increase because the 2Na+ ions will be drawn to the new base, causing Na2SO4 to disassociate further?

In which part of the reaction does the base from the new solution act?

 

[raom_dtpi]

I will rephrase the question-

Q - What happens if the basicity of a saturated solution of Na2SO4 is increased?

A- Ksp doesn't change. Additional Na2So4 will dissolve.

Reason - The saturated solution of Na2so4 is acidic since sulfuric acid will form when sulfate ions are hydrated. If the basicity of the sol is increases, additional salt will be dissolved becasue the existing protons will be netralized by the base.

Now, can someone interpret this for me!

( I am getting just the opposite that Na2so4 precipitates- The added base takes away H+ ions. So H2so4 dissociates into So4-- and H+. Now based on Le chateliers when So4-- increases, Na2So4 forms.)