Experiment 4. Acidimetric Assay by Double-Indicator Titration

unknown basic solutions

Objective of Acidimetric Assay by Double-Indicator Titration:

• To determine the percentage composition of ____________________ using double-indicator titration.

Acidimetric assay

analysis of bases using an accurately measured volume of acid

Double-indicator titration

involves the use of 2 indicators that are added subsequently in one unknown solution

Volumetric Analysis

Type of Quantitative Analysis used in the Experiments

Neutralization

Type of Volumetric Analysis used in the experiment

Direct Method

Method under Neutralization utilized in the experiment

Double-Indicator Method

• Signals the different endpoints in the given neutralization reactions

• Reactions that take place have 2 different endpoints when different indicators are used

Mixture identification

IMPORTANCE OF DOUBLE-INDICATOR METHOD:

• Samples often contain multiple bases (eg. NaOH and Na2CO3) with different strengths

• Single indicators show total neutralization; double indicators separate each base

Stepwise neutralization

IMPORTANCE OF DOUBLE-INDICATOR METHOD:

• Double indicators pinpoint each step’s endpoint for accurate measurement

Enhanced accuracy

IMPORTANCE OF DOUBLE-INDICATOR METHOD:

• Ensures precise quantification of individual base components

Direct Acidimetry

PRINCIPLES OF DOUBLE-INDICATOR TITRATION:
a. Type of Assay?

b. Type of Volumetric Analysis Method?

c. Indicator used?

a = ?

Neutralization

PRINCIPLES OF DOUBLE-INDICATOR TITRATION:
a. Type of Assay?

b. Type of Volumetric Analysis Method?

c. Indicator used?

b = ?

Pp and MO

PRINCIPLES OF DOUBLE-INDICATOR TITRATION:
a. Type of Assay?

b. Type of Volumetric Analysis Method?

c. Indicator used?

c = ?

8.0 - 10.0

COLOR OF INDICATORS IN DIFFERENT MEDIA:

Pp

a. pH range = ?

b. Acid = ?

c. Base = ?

d. Neutral = ?

a = ?

colorless

COLOR OF INDICATORS IN DIFFERENT MEDIA:

Pp

a. pH range = ?

b. Acid = ?

c. Base = ?

d. Neutral = ?

b = ?

dark pink

COLOR OF INDICATORS IN DIFFERENT MEDIA:

Pp

a. pH range = ?

b. Acid = ?

c. Base = ?

d. Neutral = ?

c = ?

light pink

COLOR OF INDICATORS IN DIFFERENT MEDIA:

Pp

a. pH range = ?

b. Acid = ?

c. Base = ?

d. Neutral = ?

d = ?

3.2 - 4.4

COLOR OF INDICATORS IN DIFFERENT MEDIA:

MO

a. pH range = ?

b. Acid = ?

c. Base = ?

d. Neutral = ?

a = ?

Red

COLOR OF INDICATORS IN DIFFERENT MEDIA:

MO

a. pH range = ?

b. Acid = ?

c. Base = ?

d. Neutral = ?

b = ?

Yellow

COLOR OF INDICATORS IN DIFFERENT MEDIA:

MO

a. pH range = ?

b. Acid = ?

c. Base = ?

d. Neutral = ?

c = ?

Salmon/Peach

COLOR OF INDICATORS IN DIFFERENT MEDIA:

MO

a. pH range = ?

b. Acid = ?

c. Base = ?

d. Neutral = ?

d = ?

Completely Neutralized

REACTIONS OF BASES UNDER DIFFERENT INDICATORS

OH-

a. Pp

b. Mo

a = ?

Completely Neutralized

REACTIONS OF BASES UNDER DIFFERENT INDICATORS

OH-

a. Pp

b. Mo

b = ?

Half-neutralized

REACTIONS OF BASES UNDER DIFFERENT INDICATORS

CO3-2

a. Pp

b. Mo

a = ?

Completely Neutralized

REACTIONS OF BASES UNDER DIFFERENT INDICATORS

CO3-2

a. Pp

b. Mo

b = ?

No Reaction

REACTIONS OF BASES UNDER DIFFERENT INDICATORS

HCO3-

a. Pp

b. Mo

a = ?

Completely Neutralized

REACTIONS OF BASES UNDER DIFFERENT INDICATORS

HCO3-

a. Pp

b. Mo

b = ?

5.0-mL of the unknown solution

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

1 = ?

20 mL of distilled water

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

2 = ?

phenolphthalein

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

3 = ?

dark pink

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

4.a. = ?

light pink

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

4.b. = ?

standard HCl solution

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

5 = ?

Record

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

6 = ?

2 drops of methyl orange

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

7 = ?

standard HCl solution

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

8 = ?

Record

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

9 = ?

composition and corresponding concentration

1. Pipet out ________________________________.

2. Add _____________________________.

3. Add 2 drops of ___________________.

4. If the color of the solution is a.__________, proceed to the next step. If it is b.________, proceed to step no. 7.

5. Titrate with ______________________ to light pink or disappearance of the pink color. (NOTE: record initial and final reading of HCl)

6. _________ the volume of standard HCl solution used.

7. To the same solution, add _______________________________.

8. Continue titration with __________________ to a salmon color endpoint. (NOTE: record initial and final reading of HCl)

9. _________ the volume of the standard HCl solution used.

10. Determine the ____________________________________ of the unknown solution from the volume of the standard HCl solution consumed during the phenolphthalein and methyl orange titrations.

10 = ?

vol Pp only

RELATIONSHIP OF BASE IDENTITY TO VOLUME OF STANDARD HCl CONSUMED:

• Pure NaOH

equal amounts of Pp and Mo (Pp = Mo)

RELATIONSHIP OF BASE IDENTITY TO VOLUME OF STANDARD HCl CONSUMED:

• Pure Na2CO3

vol Mo only

RELATIONSHIP OF BASE IDENTITY TO VOLUME OF STANDARD HCl CONSUMED:

• Pure NaHCO3

Pp is greater than Mo (Pp > Mo)

RELATIONSHIP OF BASE IDENTITY TO VOLUME OF STANDARD HCl CONSUMED:

• Mixture of NaOH and Na2CO3

Pp is less than Mo (Pp < Mo)

RELATIONSHIP OF BASE IDENTITY TO VOLUME OF STANDARD HCl CONSUMED:

• Mixture of NAHCO3 and Na2CO3

Vol HCl in Pp

TOTAL VOLUME OF STANDARD HCl CONSUMED

• Pure NaOH

Vol HCl in Pp + Vol HCl in Mo

TOTAL VOLUME OF STANDARD HCl CONSUMED

• Pure Na2CO3

Vol Mo only

TOTAL VOLUME OF STANDARD HCl CONSUMED

• Pure NaHCO3

Vol HCl in Pp - Vol HCl in Mo

TOTAL VOLUME OF STANDARD HCl CONSUMED

• Mixture of NaOH and Na2CO3

NaOH = ?

2 Vol HCl in Mo

TOTAL VOLUME OF STANDARD HCl CONSUMED

• Mixture of NaOH and Na2CO3

Na2CO3 = ?

Vol. HCl in Mo - Vol. HCl in Pp

TOTAL VOLUME OF STANDARD HCl CONSUMED

• Mixture of NaHCO3 and Na2CO3

NaHCO3 = ?

2 Vol HCl in Pp

TOTAL VOLUME OF STANDARD HCl CONSUMED

• Mixture of NaHCO3 and Na2CO3

Na2CO3 = ?

AgNO3

ANALYSIS OF ACID:

HCl

a. Reagent

b. Product

a = ?

AgCl (white ppt)

ANALYSIS OF ACID:

HCl

a. Reagent

b. Product

b = ?

BaCl2

ANALYSIS OF ACID:

H2SO4

a. Reagent

b. Product

a = ?

BaSO4 (white ppt)

ANALYSIS OF ACID:

H2SO4

a. Reagent

b. Product

b = ?

CH3CH2OH (Ethyl Alcohol) + H2SO4 (catalyst)

ANALYSIS OF ACID:

CH3COOH

a. Reagent

b. Product

a = ?

CH3COOCH2CH3 (fruity odor)

ANALYSIS OF ACID:

CH3COOH

a. Reagent

b. Product

b = ?