Question

How does room temperature cause errors in titration of a weak acid-strong base? How does impure acid/base cause errors in titration and pH readings?

Answer 1

Titration equipments is generally calibrated to be only accurate at a certain temperature.For example- the burette we use at college is calibrated at 22degree Celcius. So, the change in temperature will lead to error.

Acid- base indicators are generally temperature weak acids or bases which are temperature senstive.Apart from this, pH is changed when temperature is increased because pH is a simplified way to numerically quantify the H+ ion concentration of a given solution. Increasing in temperature also increasing the molecular vibration of concentration of [H+] ion for this decrease tendency of forming hydrogen bonds, thus leading to reduction in pH.

Impurities change in acid/base solution change the pH value.For example-Carbonate is easily formed when atmospheric carbon dioxide is absorbed by an alkaline solution. If one assumes that once the CO2 has been absorbed it remains in solution, there are two equilibria to consider.

Tirations of a weak acid (pK = 6) solution with 0.1M alkali
containing either no carbonate or a 0.1mM carbonate concentration, that is, a 0.1% carbonate contaminant. The difference between pH values (with carbonate – without carbonate) for the two titration curves rises to a maximum at the equivalence point.

A change in pH of the solution will lead to titration error.