What is back titration of aspirin?
In the back titration of aspirin, a known excess amount of NaOH is added to the sample solution to ensure that both reactions have gone to completion. Then, an additional titration is performed using HCl to determine the amount of unreacted NaOH.
Why is back titration used in aspirin?
Using titration it would be difficult to identify the end point because aspirin is a weak acid and reactions may proceed slowly. Using back titration the end-point is more easily recognised in this reaction, as it is a reaction between a strong base and a strong acid.
What is back titration?
Back titration is a titration done in reverse; instead of titrating the original sample, a known excess of standard reagent is added to the solution, and the excess is titrated.
Why 1m NaOH is used during the preparation of aspirin sample?
To determine the amount of aspirin (acetylsalicylic acid) in a sample, the precise volume and concentration of the NaOH, and the overall reaction, must be known. The NaOH serves as a secondary standard, because its concentration can change over time.
How is a back titration performed?
A back titration is a titration method where the concentration of an analyte is determined by reacting it with a known amount of excess reagent. The remaining excess reagent is then titrated with another, second reagent.
Why is back titration used instead of direct titration?
The main difference between back titration and direct titration is that a back titration determines the concentration of the unknown by determining the remaining amount of the compound with a known concentration whereas a direct titration directly measures the concentration of the unknown compound.
Which method is used in the back titration?
How much acetylsalicylic acid is in an aspirin tablet?
Each tablet contains 75 mg acetylsalicylic acid. For the full list of excipients, see section 6.1.
What percent of acetylsalicylic acid is in aspirin?
Aspirin tab- lets must contain not less than 95 percent and not more than 105 percent of the labeled amount of Cg H904 (acetylsalicylic acid). The same percentage applies for CgH9NO (acetaminophen).
What is back titration in complexometric titration?
In a back titration an excess of titrant is added to the sample. After a sufficiently long waiting time, this excess is then titrated with a second titrant. The difference between the added amount of the first and second titrant then gives the equivalent amount of the analyte.
What is the difference between a titration and back titration?
In a direct titration, you add a standard titrant to the analyte until you reach the end point. In a back titration, you add an excess of standard titrant to the analyte, and then you titrate the excess titrant to determine how much is in excess.