Why doesn't NaCl change pH but NaAc solution is basic?

[Kqwert]

Homework Statement

Hello,

I have two similar tasks here, but I don't really see any similarities in how they are "treated".

First question:

Calculate the pH of 0.01M NaCl.


Second question:

Find pH if you dissolve 0.2 mol NaAc and 0.1 mol HCl in water.

Relevant Equations

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First question:
Here they just conclude that NaCl is neither acidic or basic, and that pH is unchanged.Second question:
Here I thought that the pH would just be the concentration of HCl, as NaAc is a salt, but in the solution they instead say that H+ will combine with Ac- to form HAc. Why is these two questions different? To me they seem very similar...

 

[mjc123]

Acetic acid is a weak acid, hydrochloric acid is a strong acid.

 

[Kqwert]

Thanks! so Cl- reacting with H+ would just result in Cl- and H+ ions back again, as HCl is a strong acid? Where as for the second case H+ will react with Ac- to form, and some of the HAc will remain undissolved undissociated as it is a weak acid?

 

[mjc123]

Undissociated, not undissolved.

 

[Kqwert]

Thank you! I edited my post, is it correct now?

 

[mjc123]

Yes

 

[epenguin]

Correct, but you have not pushed anything as far as answering the questions.