Determining if the pH changes when a chemical is added

[JwdePhysics]

Homework Statement

The question asks, how many of the following statements is/ are correct. I want to know which ones are right (I don't know the answer, but I will give a guess).

1. BaCl₂ added to an HCL solution does not change the pH
2. NaBr added to an HBr solution will raise the pH.
3. NaC₂H₃O₂ added to a solution of HC₂H₃O₂ raises the pH
   
4. HNO₃ added to Ca(NO₃)₂ lowers the pH.
5. KNO₃ added to an HCL solution does not change the pH.

Homework Equations

None necessary.

The Attempt at a Solution

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Can someone tell me if my logic is right or wrong?

1. 1 is correct because the Cl^- ions are negligible bases.
   
2. 2 is incorrect because the Br^- ions are negligible bases so the pH shouldn't change
   
3. 3 is correct because the C₂H₃O₂^- ions are weak bases and adding a base to a solution increases the pH.
   
4. 4 is correct because HNO₃ is a strong acid and adding a strong acid to a solution decreases the pH. (Does it matter that number 4 doesn't specify that it is a solution?)
5. 5 I want to say is correct because KNO₃ is a nuetral salt, but I am not sure

 

[Borek]

In general and on a very basic level you are right. Wording of 4 could be better, but in general pH is a property of a solution, so if the Ca(NO₃)₂ were not dissolved in water it wouldn't make sense at all.

Sadly question is poorly thought, as it ignores some additional effects that you probably have no idea about as of yet, but which will be responsible for minute changes of pH even in those cases where the salts added are completely neutral and inert. Don't worry about it though, just be aware it is not a complete picture.

 

[epenguin]

I agree with Borek.I wondered what your three formulae in question 3 represented, but I'm guessing this is sodium acetate and acetic acid. Sodium acetate, salt of a strong base and weak acid is itself somewhat alkaline. Adding it to solution of a weak acid should increase the pH somewhat.Whereas in other cases where a salt like that is added to a strong acid the effect should be negligible.