In this experiment a polyprotic acid (here: phosphoric acid, 0.1 M) of unknown concentration but known volume is filled into a vessel. The pH electrode, after being calibrated, will be connected to the Cobra4 Mobile-Link to determine the pH value of the polyprotic acid. The solution of a strong base with known concentration (here: sodium hydroxide, 1 M) is filled into the burette. The base is added in 1 ml steps to the acid, the pH value will be determined after every step. Polyprotic acids have more than one equivalence point, therefore two individual indicators are added to the polyprotic acid solution. (here: bromcresol green, phenolphthalein).
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