[prbablydougal]

What is the ionisation enthalpy for methyl orange? and how would the pKind of methyl orange change with temp?

I am doing an A-Level chemistry project on methyl orange synthesis and analysis.
To further my investigation I have tested the effect of temperature on the pka value of my methyl orange. It seems that temperature has had no effect on my methyl orange. However surely unless the ionisation enthalpy of methyl orange is 0 the reaction is either exothermic or endothermic and therefore temperature should have an effect on the pka value of the methyl orange.
Any help would be appreciated, thank you, Dougal.