ACID-BASE Titration PART-2: Types, End Point Detection and MCQ for GPAT, GATE and CSIR NET JRF

Based on the nature of acid and base neutralization reactions are classified as :-

1.Strong acid & strong base

HCL +NaoH → NaCl + H2O

2.Strong acid & Weak base

HCl + NH4OH → NH4Cl +H2o

3. Weak acid & Strong base

CH3COOH + NaOH  → CH3COONa +H2O

4. Weak acid & Weak base 

CH3COOH + NH4OH → CH3COONH4 +H2O

Definition of Acid-base Titrations | Chegg.com

Which indicator is used in a strong acid versus a strong base ...

TITRATION :-

There are mainly two types of titration are  in acid base titrations

  1. ACIDIMETRY
  2. ALKALIMETRY

1. ACIDIMETRY :-  

Estimating an alkali solutions with a standard acid solutions is known as acidimetry. It is classified in two types

  1. Direct titration :- Acid is titrated by base. (Acid in burette base in conical flask)

  2. Residual titration :- Base reacts with large conc. of acid.Unreacted amount of acid is titrated with base.

2. ALKALIMETRY :-

 Estimating an acidic solutions with a standard base solutions is known as alkalimetry. It is classified in two types

  1. Direct titration :- Base is titrated with acid. (Base in burette acid in conical flask)

  2. Residual titration :- acid reacts with large conc. of base.Unreacted amount of base is titrated with acid.

Direct titration (Acidimetry) :-

eg. titration of Na2CO3 with HCl.

2HCl + Na2CO3 → 2NaCl + CO2 +H2O

Direct titration (Alkalimetry) :-

e.g. Assay of boric acid

H3BO3 +NaOH → NaBO2 + 2H2O

END-POINT DETECTION :-

1. Neutralization indicator :-

A. Ostwald theory :– The undissosiated indicator acid or a base has a color different than its own.

Titration Between pH at end point Commonly used indicator
Weak acid and strong base Alkaline range Thymol Blue, Phenolphthalein
Weak base and strong acid Acidic range Methyl orange, Methyl red

B. Resonance Theory :- The difference in color of the same compound in acid and base medium is apparently due to difference in structure of two forms.

pH range Acid Base
Thymol blue 1.2-2.8 red yellow
Bromocresol blue 3.0-4.6 yellow blue
Methyl orange 3.1-4.4 red orange
Methyl red 4.2-6.6 red yellow
Phenol red 6.8-8.4 yellow Red
Phenolphthalein 8.3-11.0 colorless Red

2. mixed indicator

3.universal indicator

Buffer solutions :- A solutions of substance or a mixture of substance which help in maintaing and establishing a specific pH.

pH = pka + log [conjugated base]/[conjugated acid]

This is Henderson-Hasselbalch equation which relates pH of solutions containing comparable and appreciable conc. of a conjugate acid-base pair to ratio of their concentrations.

MCQ 

1. Assay of boric acid is done by 

a.Direct titration (Alkalimetry)

b.Direct titration (Acidimetry)

c. a and b

d. None of the above

2. Resonance Theory is 

a.The same in color of the same compound in acid and base medium is apparently due to difference in structure of two forms.

b.The difference in color of the same compound in acid and base medium is apparently due to same in structure of two forms.

c.The difference in color of the different compound in acid and base medium is apparently due to difference in structure of two forms.

d.The difference in color of the same compound in acid and base medium is apparently due to difference in structure of two forms.

3.In acid base titration at pH 6.8-8.4 which indicator are used ?

a.Bromocresol blue

b.Phenol red

c.Methyl orange

d.Methyl red

4. Methyl red is give red colour at which pH ?

a.1.2-3.5

b.4.2-6.6

c.7.8-8.9

d.9.8-10.2

5. When titration occur between Weak acid and strong base which indicator are used ?

a.Thymol Blue

b. Phenolphthalein

c. a and b

d.None of the above

6.Which sentence is false about Henderson-Hasselbalch equation ?

a. It is used to determine pKa value of solutions.

b. pH of solutions containing comparable and appreciable conc. of a conjugate acid-base pair to ratio of their concentrations.

c. It is used to calculate valency of molecule.

d.pH = pka + log [conjugated base]/[conjugated acid]

7.When titration occur between Weak base and strong acid which indicator are used ?

a.Methyl orange

b.Methyl red

c. a and b

d. None of the above

8. Which sentence is false about indicator ?

a.Phenolphthalein give colourless solutions at pH 8.3-11.0 in acidic medium.

b.Methyl red  give red solutions at pH 4.2-6.6 in acidic medium.

c.Methyl orange  give orange solutions at pH 3.1-4.4 in base medium.

d.Methyl red  give red solutions at pH 4.2-6.6 in basic medium.

ANSWER KEY 

1.A

2.D

3.B

4.B

5.C

6.C

7.C

8.D

Participate in Online FREE  GPAT  TEST: CLICK HERE

  Participate in Online FREE  Pharmacist  TEST: CLICK HERE 

Participate in Online FREE  Drug Inspector  TEST: CLICK HERE

Participate in Online FREE  GATE  TEST: CLICK HERE

Participate in Online FREE  CSIR JET JRF  TEST: CLICK HERE

REFERENCE :-

VOGEL′S TEXT BOOK OF QUANTITATIVE CHEMICAL ANALYSIS FIFTH EDITION BY G.H.JEFERY, J.BASSETT (PG.NO. 262-278)

 

Leave a Reply

Your email address will not be published. Required fields are marked *

1 + 5 =

Designed & Developed by ThemeXpert