Module 9 : Experiments in Chemistry
Lecture 38 : Titrations : Acid-Base, Redox and Complexometric
38.9
 Problems
38.1)
 
1)
 Write the structures of phenolphthalein and methyl red indicators.
2)
 What is the basis of the colour changes in the indicators used in this study?
3)
 Why does phenolphthalein change colour around pH 9.0 and methyl red around pH 5.0?
4)
 Can we use a strongly acidic or basic dye as an indicator?
5)
 Is the second end point sharp? If not, how can you make it sharp?
   
38.2)
  
1)
 Explain to curves drawn for the titration of oxalic acid and H3PO4 with NaOH.
2)
 Explain the curve for the titration of Na2CO3 with HCl.
3)
 How could pK1 and pK2 of a dibasic acid be determined?
 
38.3)
 
What would be the nature of the curve for titration of
i)
 A weak acid with a strong base?
ii)
 weak acid with weak base?
iii)
 Strong acid with weak base?
iv)
 AgNO3 with NaOH?
   
38.4) List a few indicators used in EDTA titrations along with the metals they are used for and the pH at which the
  titrations are to be performed.
38.5) What are the equivalent weights of K2Cr2O7 and FeSO4 (NH4 )2SO4 .6H2O?
  How does a redox indicator function? An oxidation-reduction which has Eo nearly equal to the potential of the equivalence-point is suitable for that reaction. Explain.
   
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