Molarity of solution?

[khadcheemz]

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What is the molarity of a solution of H2SO4 if 100 ml of this solution requires 25 mL of 2 M NaOH for complete neutralization?

Isn't this N1V1=N2V2?

I thought it was 1.0 M but its .25 M

 

[clutchfans]

(2mol/L of OH-)(25mL of solution) = 0.5mmol of OH = 0.5mmol of H+
(0.5mmolH+) (1mmol H2SO4/2mmolH+) = 0.25mmol H2SO4
0.25mmolH2SO4/100mL = 0.25M of H2SO4 initial.

 

[clutchfans]

You can do it this way because NaOH is a strong base, so you can assume it dissociates 100%.
H2SO4 is a strong acid you have to assume the it also dissociates 100% twice.

 

[510586]

You can do it this way because NaOH is a strong base, so you can assume it dissociates 100%.
H2SO4 is a strong acid you have to assume the it also dissociates 100% twice.

You still do 2 N but I'm not sure if it dissociates 100% the second time.

 

[clutchfans]

You still do 2 N but I'm not sure if it dissociates 100% the second time.

Yeah, in the real world you know the second H doesn't dissociate 100% but i guess in terms of the DAT you would have to assume it does.

 

[510586]

Yeah, in the real world you know the second H doesn't dissociate 100% but i guess in terms of the DAT you would have to assume it does.

Oh ok just checking thanks. On a pH problem they could potentially ask it like that right? Then we would treat the second H as not a complete [H+] right?

 

[clutchfans]

Oh ok just checking thanks. On a pH problem they could potentially ask it like that right? Then we would treat the second H as not a complete [H+] right?

That's a really good question. I think if its a strong acid, you can assume this. If it isn't a strong acid you can't assume this.
If you have a specific question, I think it would be best to ask Dr. Romano.
Also, if they don't give you any pKa's or Ka's, your going to have to assume it dissociates twice.

 

[clutchfans]

If you have DAT destroyer, I'm sure there are a few questions like this.

 

[510586]

If you have DAT destroyer, I'm sure there are a few questions like this.

I do, but I don't recall a question involving the pH of a diprotic other than like Ba(OH)2. But I think they treated it as a total OH. Should be the same type of approach though right?

 

[clutchfans]

I would think so, but I'm not 100 percent sure.

 

[khadcheemz]

Wow that was simple! Thanks guys!

 

[clutchfans]

@khadcheemz you're welcome man.

 

[gooperwooper]

chad says that H2SO4 only fully dissociates once just fyi

 

[510586]

chad says that H2SO4 only fully dissociates once just fyi

The N would still be 2 though right?