Question

pH of an aqueous NaCl solution at 50degrees should be

Answer 1

It should be less than 7

The time when we add NaCl into water, it will completely dissociate into Na+ and Cl- ions ( salt hydrolysis ).

Parallelly water will build up it's own equilibrium

H2O → OH- + H+ K = 10^(-14 ) at 25℃

Na+ will combine with OH- whereas Cl- will combine with H+ , but as NaOH and HCl are strong base and acid simultaneously ,they will immediately dissociates into its ionic form completely

So in medium, we will have equal concentration of H+ = OH-

As per experimental data

Dissociation constant of water at 25 ℃ is

10^ (-14)= [H+] [OH-]

So at 25℃ [ H+]= [OH-] =10^(-7 )

Thus PH comes 7 at 25℃

Dissociation of water is an endothermic process ,so on increasing temperature equilibrium constant of dissociation of water will increase with temperature ,as temperature is favourable condition .

So eq. Constant for H2O will be more than >10^(-14 )

Therefore

[H+] at 50 ℃ will more than 10^(-7)

PH = -log (H+)

So for sure PH will be less than 7 .

Answer 2

The pH of the solution will lower to below 7, but the solution will remain neutral.