Back-Titration
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Back Titration - 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 tritrated with another second reagent.
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Total Mmol R = X mmol R reacted to analyte + Y mmol R, B.T (titrant)
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Example:
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A 1.00 ml alioquot of fish oil was analyzed for N using the Kjedhal Method. After digestion the distilled ammonia was collected in 100.00 ml of 0.05030 M HCl. The excess HCl required 28.30 ml of 0.1240 M NaOH for titration. Calculate the amount of N in the sample sa mg N/ml.\
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Derive the formula of Mmol R = X mmol R reacted to analyte + Y mmol R, B.T (titrant)
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X mmol R reacted to analyte = Total mmol HCl – Y mmol R B.T (titrant
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Analyte = NH3
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Reagent = HCl
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Titrant = NaOH
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X mmol R reacted to analyte = Total mmol HCl – Y mmol R B.T (titrant)
X mmol R reacted to analyte = 5.03 mmol - 3.509 mmol HCl = 1.52 mmol HCl
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1.52 mmol HCl ------> mg N
Reference and Sources:
http://www.chemteam.info/Redox/WS-redox-titration-problems.html
http://www.ausetute.com.au/redoxtitr.html
Adcvance Chemistry Notebook
Written By: Terry Maine Dela Pieza
