When an acid is titrated with a Carbonate, do we have to heat the system when Hph is the indicator? If so what is the reason?

Answer 1

If you are titrating to the first end point (about pH 8.3 or so), no, heating is not necessary. But if you are titrating to the second end point (pH about 5 or so with methyl orange or methyl red as indicator), yes. In the second case you titrate to the end point, heat to release the dissolved CO2, that raises the pH back to above the methyl red end point, then you add more titrant and you get an end point that doesn't fade.

Answer 2

Thank you!