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xii
Viva Voce in
Pharmaceutical Chemistry
Aldehydes 171
Ketones 177
Esters 179
Amides 181
Amines 184
Nitro group 189
Special reagents 191
Bibliography and Further Reading
193
1
General Questions
Q 1 What do you understand by the word ‘chemistry’?
Ans: Chemistry is the science concerned with the atomic
composition of the substances, the elements, their interactions
and the formation, decomposition and properties of
molecules.
Q 2 What is inorganic chemistry?
Ans: It is that branch of chemistry which deals with compounds
not involving covalent bonds.
Q 3 What is organic chemistry?
Ans: It is that branch of chemistry which is concerned with covalently
linked atoms, centering around carbon atoms/compounds.
Q 4 What is analytical chemistry?
Ans: It is that branch of chemistry which deals with determination
of composition, concentration, etc.
Q 5 What are the different stages of chemical analysis?
Ans: The different stages of chemical analysis are:
1. Sampling.
2. Preparation of analytical sample, e.g. reduction of particle size,
mixing for homogeneity, drying, determination of sample
weight or volume.
3. Dissolution of sample, e.g. using solvents, by heating, ignition,
dilution.
4. Removal of interferences: By filtration, solvent extraction, ion
exchange, chromatographic separation.
5. Sample measurement and control of instrumental factors:
During standardisation, calibration, optimisation.
6. Results: Calculation of analytical results, statistical evaluation
of data.
2
Viva Voce in
Pharmaceutical Chemistry
7. Presentation of data: In the form of practical records, data
plotting, storage (archiving).
Q 6 How are analytical methods classified?
Ans: On the basis of sample size, analytical methods are classified
as follows:
1. Macro: For quantities of 0.1 g or more.
2. Semimicro or Meso: For quantities ranging from 10
–2
g to 10
–1
g.
3. Micro: For quantities in the range of 10
–3
g to 10
–2
g.
4. Submicro: For quantities in the range of 10
–4
g to 10
–3
g.
5. Ultramicro: For quantities below 10
–4
g.
Q 7 What is chemical analysis?
Ans: Chemical analysis is the application of a process or series of
processes in order to identify and/or quantify a substance,
the components or solutions or mixture, or the determination
of structures of chemical compounds.
Q 8 What is qualitative analysis?
Ans: Qualitative analysis is the application of a process or series of
processes to ascertain/identify the substances or impurities
present in the chemical compound. It may also include analysis
to confirm that certain specified impurities are absent.
Q 9 What is quantitative analysis?
Ans: The process/processes adopted to determine how much of
each compound or a specified component is present is called
quantitative analysis. This includes determination of
composition and purity.
Q 10 What is assaying?
Ans: A quantitative analysis performed to establish the proportion
of the essential component is called assaying.
Q 11 What is quality control?
Ans: Analysis of final product to ensure that the essential compo-
nents are present within the predetermined range of composi-
tion and the impurities do not exceed the specified limit is called
quality control.
Q 12 What is analytical grade chemical?
Ans: AR or Analytical reagent implies that the chemical is of a high
degree of purity wherein limits of various impurities are
known and are below the limits stated in Indian Pharma-
copoeia.
General Questions 3
Q 13 What is laboratory reagent (LR)?
Ans: Laboratory reagent grade implies that it is chemically pure
grade material, which is not necessarily required to be tested
for limiting or absence of certain impurities.
Q 14 Which reagents are more pure, LR or AR?
Ans: Analytical reagents (ARs) are more pure than laboratory
reagents (LRs).
Q 15 Which solvents can be used for dissolving inorganic sub-
stances?
Ans: Many inorganic substances can be dissolved directly in water
or in dilute acids. But materials such as minerals and alloys
need to be tested with variety of reagents in order to discover
suitable solvent. Concentrated acids can be used to dissolve
many metals and metallic oxides.
Q 16 What are the different kinds of water used in the field of
pharmacy?
Ans: Purified water, carbon dioxide free water, water for injection,
sterile water for injection, and deionised water.
Q 17 Which kind of water is suitable for laboratory use in chemistry?
Ans: Purified water is essential for laboratory use. The level of
purity required in purified water depends upon instrumental
method of analysis. Normally, purified water is prepared by
distillation of tap water, by deionisation or by reverse osmosis.
Q 18 Name few flammable common solvents used in the laboratory.
Ans: Methanol, ethanol, benzene, toluene, acetone, and ether.
Q 19 Name five strong bases used in the laboratory.
Ans: Sodium hydroxide, potassium hydroxide, calcium hydroxide,
concentrated ammonia solution and sodamide.
Q 20 Enlist inorganic acids used in chemistry practicals.
Ans: Hydrochloric acid, sulphuric acid, nitric acid, perchloric acid,
hydrobromic acid, etc. are used in chemistry practicals.
Q 21 Enlist three organic acids which are liquid in nature.
Ans: Formic acid, acetic acid and lactic acid are the organic acids
which are liquid in nature.
Q 22 What precautions should be taken while diluting the
concentrated sulphuric acid?
Ans: Sulphuric acid should be mixed with water very carefully, by
pouring it into cold water, as a thin stream, to prevent acid
splashes or spray.
4
Viva Voce in
Pharmaceutical Chemistry
Q 23 Name few chemicals with obnoxious odour.
Ans: Pyridine, benzoyl chloride, isocyanides, etc. have obnoxious
odour.
Q 24 Name some hazardous chemicals.
Ans: Hazardous chemicals used in the laboratory are:
• Concentrated acids
• Liquid bromine
• Pottassium cyanide
• Benzoyl chloride
• Hydrogen cyanide gas
• Sodium metal, etc.
Q 25 Name an organic compound which is explosive.
Ans: Following chemicals are explosive in nature.
• Ammonium nitrate
• The nitrate esters of polyhydric alcohols
• Concentrated hydrogen peroxide solution
Q 26 What care should be taken while using the reagents?
Ans:
1. Take care that every reagent or solution you prepare is
properly labeled.
2. After use the stopper should be placed to the respective
reagent bottle only and must not be placed on the bench.
3. The reagent bottles should be replaced to their original
positions on the shelf immediately after use.
Q 27 Enumerate different ways of expressing percentage.
Ans: There are four ways of expressing percentage:
• w/v (weight by volume) %
• v/w (volume by weight) %
• v/v (volume by volume) %
• w/w (weight by weight) %
Q 28 What do you understand by 5% w/v solution?
Ans: It indicates that 5 g of the solute is dissolved to produce 100 ml
of the solution.
Q 29 What is the meaning of 5% v/v solution?
Ans: It means 5 ml of the liquid is mixed with solvent to produce
100 ml of the solution.
General Questions 5
Q 30 What is the meaning of 5% w/w percentage?
Ans: It means 5 g of substance is mixed with diluent to produce
100 g of mixture.
Q 31 What is the meaning of 5% v/w percentage?
Ans: It indicates 5 ml of the liquid is mixed with a solid to produce
100 g of the mixture.
LABORATORY APPARATUS, CLEANING AND CALIBRATION
Q 32 Name the glass apparatus used in inorganic pharmaceutical
chemistry practical.
Ans: Burettes, pipettes, conical flask, beaker, measuring cylinder,
volumetric flask, round bottom flask, funnel, test tube,
Nessler’s cylinder, reagent bottle, weighing bottle are some
of the glass apparatus used in pharmaceutical chemistry
laboratory.
Q 33 Which type of glass is used to prepare glassware used in
chemistry laboratory? Why?
Ans: Borosilicate glass is used for making the glasswares in
chemistry laboratory. Borosilicate glass is preferred because
it is a resistant glass which is very slightly affected by chemical
solutions. This glass is also resistant to heat and thus solutions
can be heated in the glass apparatus.
Q 34 How should the glass apparatus be cleaned?
Ans: Glass apparatus is cleaned using commercially available
detergent powders or solutions.
Q 35 How would you clean stubborn dirt or chemical from the
glass apparatus?
Ans: Stubborn dirt or chemical from the glass apparatus can be
cleaned by filling the apparatus with chromic acid cleaning
mixture. Allow to stand for some time and pour off the
chromic acid solution and then rinse with deionised water.
Allow to drain until dry.
Q 36 What is cleaning mixture?
Ans: It is a saturated solution of powdered sodium dichromate or
potassium dichromate in concentrated sulphuric acid. Sodium
dichromate is much more soluble than potassium dichromate.
So, sodium dichromate is preferred.
6
Viva Voce in
Pharmaceutical Chemistry
Q 37 How cleaning mixture is prepared?
Ans: Dissolve 5 g of powdered sodium dichromate in 5 ml of water
in a 250 ml beaker and add 100 ml of conc. sulphuric acid
carefully with constant stirring.
Q 38 What is aqua regia?
Ans: Aqua regia is 75 vol % hydrochloric acid and 25 vol % nitric
acid. Due to its oxidising character, it is very potent solvent.
Other oxidants like bromine and hydrogen peroxide further
increase the effectiveness.
Q 39 How would you ensure the cleanliness of glass apparatus?
Ans: Fill the glass apparatus with distilled water and remove the
water. If an unbroken film of water remains in the glass
apparatus, it is clean. If water remains as drops or as broken
film, the apparatus is dirty.
Q 40 What do you understand by volumetric apparatus?
Ans: It is the glassware used for accurate measurement of volumes
of solution. The volumetric apparatus is appropriately
graduated to indicate their total or partial capacities.
Q 41 Enlist the volumetric apparatus used in chemistry practicals.
Ans: Burette, pipette, measuring cylinder, volumetric flask.
Q 42 Name the units of volume as per metric system.
Ans: 1 L = 1000 ml
1 ml = 1000 µl
One litre is the volume occupied by 1 kg of water at 4°C
1 Litre = 1.000028 dm
3
1 ml = 1.000028 cm
3
Q 43 Describe different types of pipettes.
Ans: There are three kinds of pipettes:
1. Transfer pipettes: They have one mark and deliver constant
volume of liquid under specified conditions.
2. Graduated or measuring pipettes: They have graduated
stems and are employed to deliver various small volumes as
required.
3. Syringe pipettes or micropipettes: They have fixed or variable
volume. They are used for dispensing toxic solutions or small
volumes or large numbers of repeat volumes for multiple
analysis. They can deliver volumes of 1 µl to 10 ml.
General Questions 7
Q 44 Differentiate volumetric pipette and graduated pipette.
Ans: With volumetric pipette specified constant volume of the
liquid can be measured while with graduated pipette various
small volumes can be measured and delivered.
Q 45 How should be the liquid transferred using pipette?
Ans:
1. A suitable pipette filler is attached to the suction tube.
2. Rinse the pipette with a small amount of liquid to be transferred
and then discard it.
3. Fill the pipette with the liquid to about 1–2 cm above the
graduation mark.
4. Wipe the lower stem with a piece of filter paper.
5. Allow the liquid to run out slowly until the bottom of the
meniscus reaches the desired graduation mark.
6. The pipette must be held vertical and with graduation mark
at eye level.
7. If the total volume is to be taken then any drop adhering to the
tip is removed by stroking against a glass surface. Hold the tip
in contact of glass surface, for a draining time of 15 seconds.
Q 46 What precaution one must take while using a pipette?
Ans: The filling of pipettes should never be carried out by mouth
suction and the pipette should never be placed to the lips,
irrespective of which liquid is being measured.
Q 47 How to take correct reading while using a burette?
Ans: While reading the position of the meniscus, the eye must be
at the same level of the meniscus, to avoid the errors due to
parallax. The graduation mark matching with lower miniscus
is the desired reading, for colourless solutions.
Q 48 What do you understand by calibration?
Ans: Calibration is necessary to determine accurate capacity of the
graduated apparatus. Calibration is the process of standar-
dizing any measuring (graduated) instrument, glassware,
procedure, etc.
Q 49 How calibration of graduated apparatus is done?
Ans: Calibration procedure involves determining the weight of
water contained in or delivered by the particular piece of appa-
ratus, at a specific temperature. From the known density of
water at that temperature, volume of water can be calculated.
8
Viva Voce in
Pharmaceutical Chemistry
Q 50 Describe the calibration process for pipette.
Ans:
1. Clean the pipette thoroughly and dry. Keep it near the balance
for 1 hr.
2. Clean the weighing bottle and dry. Keep it near the balance
for 1 hr.
3. Keep the liquid (water) near the balance for 1 hr, so that all
the apparatus has same temperature.
4. Measure the volume of the liquid using pipette as per the
standard procedure.
5. Weigh the contents after closing the weighing bottle.
6. Take the temperature of water.
7. Calculate the volume from the density table for that tempera-
ture.
Q 51 How to calibrate other graduated apparatus?
Ans: Same basic principle as that applied for pipette calibration is
applicable for other graduated apparatus like graduated flask,
burette, etc.
Q 52 What is a desiccator?
Ans: A desiccator is a covered glass container designed for the
storage of chemicals/objects in a dry atmosphere. Inside this
glass container, the base is a drying agent, such as anhydrous
calcium chloride, silica gel, activated alumina or anhydrous
calcium sulphate.
Q 53 What are self-indicating drying agents?
Ans: Silica gel, alumina and calcium sulphate can be impregnated
with cobalt salt to make them self-indicating. Initially, the
colour is blue and when the desiccant is exhausted (due to
absorption of moisture), it becomes pink.
Q 54 How the desiccant is regenerated?
Ans: The pink coloured exhausted desiccant can be regenerated
by heating in an electric oven at 150–180°C (silica gel), 200–
300°C (activated alumina), 230–250°C (calcium sulphate).
Q 55 Name the heating apparatus used in the laboratory.
Ans: Burners, hot plates, electric ovens, microwave ovens, muffle
furnaces, heating mantles are some heating apparatus used
in the laboratory.
General Questions 9
WEIGHING
Q 56 What do you understand by ‘weight’ of a substance?
Ans: The weight of the material is the force of attraction due to
gravity that is exerted upon the object.
w = mg, where w is weight, m is mass and g is acceleration
due to gravity.
Q 57 Name the units of weight used as per metric system.
Ans: 1 kg = 1000 g
1 g = 1000 mg
1 mg = 1000 µg
Q 58 How many mg are there in 1 kg?
Ans: 1000000 mg, i.e. 1 million mg make 1 kg.
Q 59 What do you understand by the term ‘weighing balance’ ?
Ans: It is an instrument employed for determining relative
weights of substances or for weighing the substance under
consideration.
Q 60 Enlist the types of balances used in weighing.
Ans: There are various balances with difference in weighing capability
and sensitivity.
1. Physical balance — generally employed in pharmaceutics
practical for rough weighing.
2. Analytical balance — employed in analytical chemistry practicals.
3. Triple beam balance.
4. Torsion type balance.
5. Single pan electronic balance.
6. Platform electronic balance.
Q 61 State the meaning of analytical balance.
Ans: Analytical balance or chemical balance is the balance
employed for analytical purposes with maximum load
capacity of 100 to 200 g and a sensitivity of 0.1 mg.
Q 62 What are the important parts of analytical balance?
Ans: The main parts are:
1. Graduated beam supported on pillar
2. Pans
3. Pointer
4. Knob or key