WHICH METHOD IS THE BEST FOR DETERMININGudTHE END-POINT IN STRONG ACID – STRONG BASE TITRATIONS: USING A PH INDICATOR, MEASURING TEMPERATURE CHANGE, OR MEASURING RESISTANCE?

摘要

In this essay, three of the methods for finding the end-point in acid-base titrations areudexamined and compared. The titration is done with 0.1 molar NaOH as the titrant and 0.1udmolar HCl as the analyte. The methods are: Using phenolphthalein as an indicator, measuringudthe temperature change, measuring the resistance of the analyte. The goal is to determineudwhich method among these three is the most accurate, in order to find out which method canudbe used in the absence of a pH meter.udIn each method, a pH meter is also used to see the actual pH when the method comesudto the end-point. The variables for each experiment are graphed, together with pH, and then atudthe end-point of the methods the pH is found using graphing software. The mean values forudeach method are calculated and compared with the literature value of the equivalence pointudfor this titration, which is 7. The indicator method is proved to be the best among these threeudwith a very low error percentage, the resistance method comes second, however it has a highuderror percentage and is not very appropriate for using in this titration. The temperature methoduddid not give any sign of reaching the end-point; therefore its error percentage could not beudcalculated and proved that it is not suitable for this titration. For titrations with differentudconditions all the methods have to be tested again before deciding which is the best.udTo sum up, amongst these methods, using phenolphthalein as an indicator of the endpointudis the best method to use in the absence of a pH meter, for this acid-base titration.