Citric acid has $\mathrm{p}K_\mathrm{a}$-values of 3.1, 4.7, and 6.4, while those of tartaric acid are 3.0 and 4.3. If you adjust the $\mathrm{pH}$ to 6.4, tartaric acid would be roughly 100% deprotonated, while 50% of citric acid still has one proton to give off. If you titrate this solution with $\ce{NaOH},$ you could estimate the buffer capacity, giving ...


I am afraid the measurement of the pH at half titration does not give a useful information on the pKa. There has been a detailed series of measurements of the pH at half titration for different concentrations of phosphoric acid. See Cecile Canlet, BUP 938, 1, p. 1129, November 2011. For the first H atom, the theoretical pKa should be 2.12. But the pH ...


The mass of a particular isotope is determined by mass spectrometry. Hopefully you know this technique. In order to obtain a high degree of precision, the beam must go through several mass spectrometers coupled in series, some of which are quadrupoles or octupoles. It would take hours to explain the developments of this technique.

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