This document provides answers to 30 common chemistry interview questions. It defines terms like pH, aliquot, diluent, and titration. It describes the four types of titrations and summarizes the principles and applications of techniques like UV spectroscopy, infrared spectroscopy, HPLC, and chromatography. Key terms are also defined, such as molarity, molality, stability indicating assay method, and mass balance.

1. Most Common Chemistry Interview
Question and Answers
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2. 1. What is the body temperature ?
Ans: 37 °Celsius or 98.6° F
2. Define pH ? What is the pH of blood ?
Ans: pH- Negative logarithm of hydrogen ion concentration.
Blood pH - 7.35 to 7.45
3. Explain the term aliquot and diluents ?
Ans: Aliquot: a measured sub-volume of original sample.
Diluent: Material with which the sample is diluted.

3. 4. Explain what is titration ?
Ans: Titration ( also known as volumetric analysis) is a quantitative chemical
analysis to determine the concentration of an identified analyte. A reagent termed
the titrant or titrator is prepared as a standard solution of known concentration
and volume. The titrant reacts with a solution of analyte to determine the analytes
concentration the volume of titrant that reacted with the analyte is termed the
titration volume.
5. What are the types of titrations ?
Ans: There are four types of titrations
1. Acid base titration: In which an acidic or basic titrant reacts with an analyte
that is a base or an acid.
2. Complexo metric titrations: Involving a metal- ligand complexation reactions.
3. Precipitation titrations: In which the analyte and titrant react to form a
precipitate.
4. Redox titration: Where the titrant is an oxidizing or reducing agent.
6. What is room temperature?
Ans: 25 degree centigrade
7. What is the Ultraviolet(Uv) and Visible Spectroscopy Range?
Ans: Uv spectroscopy range 200-400nm, Visible spectroscopy range 400-800nm.

4. 8. What is Osmosis ?
Ans: A process by which molecules of a solvent tend to pass through a semi
permeable from a less concentrated solution into a more concentrated one.
9. What is the use of UV Spectroscopy ?
Ans: Spectroscopy used for detecting the functional groups, impurities ;
Qualitative and Quantitative analysis can be done.
10. What is the difference between Qualitative and Quantitative analysis ?
Ans: Qualitative analysis involves identification of the compound or
chemical based on their chemical ( absorption or emission) or physical
properties (e.g, melting point, boiling point).
Quantitative analysis: involves estimation or determination of concentration
or amount of the chemical compounds or components.
11. Expand LCMS, HPLC,UPLC, TLC, and GC ?
Ans: LCMS- Liquid Chromatography
HPLC- High Performance Liquid Chromatography
UPLC-Ultra High Performances Liquid Chromatography
TLC-Thin Layer Chromatography
GC-Gas Chromatography

5. 12. Explain the principle of Ultraviolet Spectroscopy ?
Ans: Uv spectrsocopy uses light in the UV part of electromagnetic spectrum. Uv
absorption spectra arises in which molecule or atoms outer electrons absorb
energy, undergoes transition from lower energy level to higher energy level. For
each molecules absorbance at wave length is specific.
13. Explain about Beer Lambert Law ?
Ans: It states that the intensity of monochromatic light absorbed by a substances
dissolved in a fully transmitting solvent is directly proportional to the substance
concentration and the path length of the light through the solution.
14.Explain the Infrared Spectroscopy principle ?
Ans: When a molecule absorbs the infrared radiation, it vibrates and gives rise to
packet Infrared(IR) absorption spectrum. This IR spectrum is specific for every
different molecule absorption to identification of functional groups.
15. Explain the difference between QC and QA ?
Ans: QA provides the confidence that a product will full fill the quality
requirements. QC determines and measures the product quality level.

6. 16. Expand IQ,OQ,PQ,DQ ?
Ans: IQ- Installation Qualification
OQ-Operational Qualification
PQ- Performance Qualification
DQ- Design Qualification
17.What is the HPLC principle ?
Ans: It is a technique used for separating the mixture of components into individual
components based on absorption, partition, ion exchange and size exclusion
principles. Stationary phase and mobile phase used in it. HPLC used for
identification, quantification and purification of components form a mixture.
18.Explain HPLC Instrumentation ?
Ans: It involves solvent system, pump, sample injector, HPLC columns, Detector
and recorder. Firstly solvent (mobile phase) is degassed for eliminating the bubbles.
It is passes through the pump with a uniform pressure. The liquid sample is injected
into the mobile phase flow stream. It passes through the stationary phase identified
by the detector and recorded.
19. In reverse phase HPLC, Which type of stationary phase is used and give
example?
Ans: Non polar stationary phase used ex: silica gel C-18.

7. 20. What are the detectors used in HPLC ?
Ans: Uv detector, IR detector, Fluorescence detector, mass spectroscopy, Lcms etc.
21. Who to calculate retension factor in paper chromatography?
Ans:
Rf= Distance travelled by solute/ Distance travelled by solvent
22. Define Molarity ?
Ans: Number of moles of solute per litre solution.
Denote by “ N”.
23. Define Molality ?
Ans: Number of moles of solute per kilogram solvent.
Denote by “m”.
24. Define “ DRUG” ?
Ans: A substance intended for use in the diagnosis, cure, mitigation, (reduction of
pain), treatment or prevention of disease.

8. 25. Expand NOEL, MACO, CAPA, QMS, OoS, OoE ?
Ans:
NOEL- No observed effect level
MACO-Maximum Allowable carry over
CAPA- Corrective action and preventive action
QMS- Quality Management system
Oos- Out of specification
OoE- Out of exception
26. Why phosphate buffer generally used in Rp chromatography ?
Ans: Because it has three protonated forms as H3PO4, H2PO4 & HPO4
2
which has 3pka values 2.7 & 12 respectively.
27. What is stability indicating assay method ?
Ans: It is qualitative analytical method it can detect any change with time.
28. What is “mass balance” ?
Ans: Any increasing in degredent value is indicated by corresponding drop in
assay value.

9. 29. What is difference between assay & potency ?
Ans: Potency: It is purity of compound which states the % available of main
compound without water and residual solvent.
Assay: It is define as potency + water an residual solvent.
Assay and potency are same when assay expressed as is basis.
30. What is elution order for acidic & basic compound in chromatography?
Ans: Acids have maximum retention at lower pH and base have minimum retention
at lower pH as they are fully charged. This order is vice versa at higher pH.

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