Module 3: ACID-BASE TITRIMETRY: TITER VALUES; RESIDUAL TITRATION (Assay of Magnesium hydroxide content of Milk of Magnesia by Residual Titration)

Question 1

• Antacid suspension
  – White viscous liquid
• Active:
  – Magnesium hydroxide,
  Mg(OH)2
• Common side effect:
  – Diarrhea

Answer 1

Milk of Magnesia (MOM)

Question 2

• Antacid suspension
  – White viscous liquid

Answer 2

Milk of Magnesia (MOM)

Question 3

• Active:
  – Magnesium hydroxide,

Answer 3

Milk of Magnesia (MOM)

Question 4

end point of Assay of MOM

Answer 4

yellow color

Question 4

Assay of Milk of Magnesia (MOM)
* Standard Solutions:?

Answer 4

0.1 N NaOH (from M2 L4)
0.1 N H2SO4 (from M2 L2)

Question 5

Assay of Milk of Magnesia (MOM)
* Type and Methods:?

Answer 5

Residual Acidimetry

Question 5

Assay of Milk of Magnesia (MOM)

Answer 5

xs Acid + Baseanalyte → unreacted Acid

Question 6

indicator

Answer 6

methyl red

Question 6

Assay of Milk of Magnesia (MOM)
* Titrant:?

Answer 6

0.1 N NaOH

Question 7

Assay of Milk of Magnesia (MOM)
* Analyte:?

Answer 7

Magnesium hydroxide,
Mg(OH)2

Question 7

Assay of Milk of Magnesia (MOM)
* Indicator:?

Answer 7

Methyl red

Question 7

Assay of Milk of Magnesia (MOM)
* Endpoint:?

Answer 7

Yellow (slightly turbid)

Question 8

Assay of Milk of Magnesia (MOM)
* USP limit:?

Answer 8

7 – 8.5%

Question 8

%𝑨 formula

Answer 8

%𝑨 =
𝑵𝒙𝒔𝑽𝒙𝒔 − 𝑵𝒕𝑽𝒕 𝒙 𝒎𝑬𝒒 𝒘𝒕
————————————— 𝒙 𝟏𝟎𝟎
𝒈𝒔𝒙

𝒙𝒔 → 𝒆𝒙𝒄𝒆𝒔𝒔 𝒕 → 𝒕𝒊𝒕𝒓𝒂𝒏𝒕

*Used to determine the “%content or purity” of a substance (analyte) in a given sample using residual or back titration

Question 9

ASSAY (Residual)

Analyte:
Titrant:
Excess:

Answer 9

Analyte: Acid
Titrant: Acid
Excess: Base

Question 10

ASSAY (Residual)

Analyte:
Titrant:
Excess:

Answer 10

Analyte: Base
Titrant: Base
Excess: Acid

Question 10

– Before substitution, identify the titrant and excess based on the nature of analyte.
= Mg(OH)2
= NaOH
= H2SO4

Answer 10

• Analyte: Mg(OH)2 (base)
• Titrant: NaOH (base)
• Excess: H2SO4 (acid)