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.
What is back titration explain?
Updated on October 07, 2019. 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.
What is titration of aspirin?
A titration is a lab process where substances are combined using volumetric glassware, such as buret, in a carefully controlled way such that the exact amounts needed to react are used. You already know from the Bonding Lab, that aspirin is weak electrolyte.
Why aspirin is determined by back titration method?
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.
How do you calculate back titration?
5 Simple Steps in Back Titration Calculations:
- Determine the amount of C required in the titration.
- Using stoichiometry, find the amount of A that reacted with C in the titration.
- Note that amount of A that reacted with C in the titration = amount of A that did not react with B in the earlier reaction.
Why is it called back titration?
Back titration is also titration. It is called back titration because it is not carried out with the solution whose concentration is required to be known (analyte) as in the case of normal or forward titration, but with the excess volume of reactant which has been left over after completing reaction with the analyte.
Why do we titrate aspirin?
Assuming the aspirin is not contaminated with other acids, the titration allows you to quantitatively determine the purity of your aspirin. (The reacting hydrogen is circled in the equation below.) NaOH is corrosive.
Where is back titration used?
Back titrations are mainly used in the following cases: if the analyte is volatile (e.g., NH3) or an insoluble salt (e.g., Li2CO3) if the reaction between analyte A and titrant T is too slow for a practical direct titration.
How do you calculate the theoretical yield of aspirin?
Using the theoretical and actual you can calculate percent yield.
- Actual Yield of Aspirin in lab after filtered/dried (mock value) = 370 g.
- Mass of Theoretical Yield of Aspirin (mock value) = 360.3 g.
- Percent Yield = (Actual ÷ Theoretical) x 100 = (370 ÷ 360.3) x 100 = 103 %
What is back and 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.
What type of reaction is aspirin synthesis?
esterification reaction
The synthesis of aspirin is known in organic chemistry as an esterification reaction. This is a substitution reaction in which an alcohol (the –OH group in salicylic acid) reacts with acetic anhydride to form an ester, aspirin.
How do you calculate moles of aspirin?
Calculate the moles of substance by dividing the mass of substance in grams by the molecular weight in amu. In this case, the aspirin tablet contains 250 mg, or 0.250 g. Therefore, 0.250 g ÷ 180.17 amu = 0.00139 moles of aspirin.
What is back titration in complexometric titration?
A back titration is used, where an excess of bismuth nitrate is added to the sample, bismuth phosphate is then precipitated and unreacted bismuth ions are titrated against EDTA.
How do you do a back titration?
Can You Back titrate aspirin?
This experiment is designed to illustrate techniques used in a typical indirect or back titration. You will use the NaOH you standardized last week to back titrate an aspirin solution and determine the concentration of aspirin in a typical analgesic tablet. You will be graded on your accuracy.
What is the titration method for aspirin?
You cannot use simple titration method since aspirin is a weak acid, the identification of the endpoint will get difficult and the reaction will proceed slowly. The ‘stage one’ of this reaction is of alkaline hydrolysis involving reaction of aspirin solution with a measured amount of sodium hydroxide.
What is back titration?
This text is available online and is used for guidance and inspiration Back titration was the method used to determine the concentration of aspirin by reacting it with known amount of excess base.
How can I determine the concentration of aspirin in a tablet?
use the NaOH you standardized last week to back titrate an aspirin solution and determine the concentration of aspirin in a typical analgesic tablet. You will be graded on your accuracy. D. Harris, Quantitative Chemical Analysis ( 7th ed., W. H. Freeman, NY, 2007) p. 121-122.