[ARGOS++]

Dear Angelku;

Maybe? a little bit simpler:

That’s because for CaCO₃ as an Example, and/at the given End Point:
   CaCO₃     +  H₂SO₄  --->  CaSO₄ +   H₂O + CO_2(g) .
 
And that would be quasi equivalent to:
    Ca(OH)₂  +  H₂SO₄  --->  CaSO₄ + 2H₂O
(because CO_2(g) has left the System.)

I hope it may be of help.


Good Luck!
                    ARGOS⁺⁺

[AWK]

At ph 8 CO2 do not left the system!

[ARGOS++]

Dear Mr. AWK;

That’s precisely why I was also talking about Indicators and/at the given End Point: Not pH 8!
(Please see the previous posts.)

Good Luck!
                    ARGOS⁺⁺

[AWK]

But Angelku use the phenol red indicator, and just its using practically prevents decomposition of CaCO3.

[ARGOS++]

Dear Mr. AWK;

I’m surprised!,  ─   Something below pH 6.6?:   "Phenol Red”

Good Luck!
                    ARGOS⁺⁺

[AWK]

When we titrate from basic side?

[ARGOS++]

Dear Mr. AWK;

Sorry!,  ─   Exactly in this case Phenol Red changes from Red to Yellow and so our Endpoint will lie at, or below pH 6.6!
(Not only Wiki is telling that.)

Good Luck!
                    ARGOS⁺⁺

[angelku]

How about using phenolphthalein as an indicator?Its pH is 8.2-10.0.

Is is calcium carbonate in the solution have already completely decompose into CO2 which left to the system at pH below 7?Do you mean H2SO4 needed to be use for neutralising the additional amount of CO2 presence in the solution no matter the CO2 left or not?
I
Although the  CO2 leave the system at pH below 7,more amount of H2SO4 still needed to be used even the end point is at pH above 8.Am I right?
 

[ARGOS++]

Dear Angelku;

Cheer!,  ─   You are very Solomonic, and you learn quite fast/well, but how is it called in English (American):  “TANSTAAFL”.

If the CO_2(g) from CaCO₃ doesn’t leave the System, then also all the CO_2(g) you picked up during hydrolysis, during dilution, and during titration will not leave the System either.
In such case you will find a too small value of H₂SO₄, now simulating a too high content of Aspirin!

Quintessence: 
You can’t make a method more specific as it is by its nature,   ─   You have to live with.
(But you can combine/change methods!)

Good Luck!
                    ARGOS⁺⁺

[AWK]

How about using phenolphthalein as an indicator?Its pH is 8.2-10.0.

Is is calcium carbonate in the solution have already completely decompose into CO2 which left to the system at pH below 7?Do you mean H2SO4 needed to be use for neutralising the additional amount of CO2 presence in the solution no matter the CO2 left or not?
I
Although the  CO2 leave the system at pH below 7,more amount of H2SO4 still needed to be used even the end point is at pH above 8.Am I right?
 

I think phenolphtalein is a good idea. It change color (become colorlees) just 0.1 pH unit over pH of NaHCO3 hydrolysis

[ARGOS++]

Dear Mr. AWK;

I don’t understand:   ─   A good Idea?   ─   For what?

─  For the evidence that the CO₂  will not leave the system and we titrate a more or less erroneous actual content?

─  Or that we Chemists are so genial that we are able to titrate with a visual precision of better then 0.1 pH Units with the help of an indicator with its well known problems at acidic end of its indication range?

I don’t believe that continuing such discussions are doing any good job/help for anybody who tries to learn,  ─  Sorry!

Good Luck!
                    ARGOS⁺⁺