Quality control interview
Question.1) What is volumetric or titrimetric analysis.?
Answer: It consists of determination of volume of solution of accurately known concentration required to react completely with the solution or substance to be determined.
Question.2) What is standard solution.?
Answer: A solution of accurately known strength is known as standard solution, standard solution are usually expressed in terms of molarity or normality.
Type of standard solution:
a) Primary standard
b) Secondary standard
Question.3) What is primary standard solution.?
Answer: Primary standard is a chemical or reagents which has certain properties such as:
- It is extremely pure
- Highly stable
- It is anhydrous
- It is less hydroscopic
- Has very high molecular weight
- Can be weighed easily
- Should be ready to use and available
- Should be preferably non toxic
- Should not be expensive
Question.4) What is extremely pure standard.?
Answer: Primary standard should be extremely pure which means that, it should be a chemical of high grade of purity, preferably 99.98%
Question.5) What is meaning of primary standard stability.?
Answer: It should be highly stable which means it usually does not react easily when kept in its pure form or in other words it should have very low reactivity.
Question.6) What is importance of stability in primary standard.?
Answer: If a reagent reacts easily with atmospheric oxygen or water or changes its property over time then it is unreliable chemical to use as primary standard.
Question.7) What is importance of anhydrous in primary standard.?
Answer: It should be anhydrous which means that it does not contain any water molecule in its molecular structure.
For Example: Magnesium sulphate (MgSO4) is found with formula MgSO4.7H2O. Therefore, to prepare primary standard solution of MgSO4, anhydrous MgSO4 preferably of analytical grade with purity greater than 99.98% will be required.
Question.8) What is importance of less hydroscopic in primary standard.?
Answer: The chemical preferably should be less hydroscopic that is on opening the container it should not absorb water molecules from atmosphere.
Question.9) What is importance of high molecular weight in primary standard.?
Answer: It should have very high molecular weight to minimize weighing errors.
Question.10) What is use of primary standard.?
Answer: The following use of primary standards.
- Use of standardize a volumetric solution.
- They are used for standardization of titration solution.
- They are used for calibration of secondary standards.
- Used as reference to determine unknown concentrations or to calibrate an analytical instruments.
Question.11) What is Secondary standard.?
Answer: A secondary standard is a solution which contain exactly known amount of the substance in unit volume of the solution which is determined by titrating against a primary standard.
Question.12) What is properties secondary standard.?
Answer: A secondary standard is a chemical or reagent which has certain properties such as:
- It has less purity than primary standard.
- Less stable and more reactive than primary standard.
- But its solution remains stable a long time.
- Titrated against primary standard.
Question.13) What is uses of secondary standard.?
Answer: Secondary standard use as following.
- Secondary standard are commonly used to calibrate analytical equipment and analytical techniques.
- Used in titration.
Question.14) What is titrate.?
Answer: The substance being titrated taken in conical flask is known as titrate.
Question.15) What is titrant.?
Answer: The solution of known concentration used in titration which is added from burette are known as titrant.
Question.16) What is end or equivalent point.?
Answer: The point at which reaction between titrate and titrant is just complete indicated by a change in color of indicator is called as endpoint or equivalence point. For example after titration the color of the substance changes due to reaction completion.
Question.17) What is titration.?
Answer: The process of addition of standard solution from burette into the solution of unknown concentration taken in the conical flask is known as titration.
Question.18) What is indicator?.
Answer: It is a complex organic compound which shows clear visual change after the reaction between titrant and titrate is just complete for example Phenolphthalein, Methyl orange, Thymol blue and methyl red.
Question.19) What is titration error.?
Answer: In practice very small difference between theoretical endpoint and actual endpoint usually occurs it is known as titration error example suppose experimental value is 5.10 and actual value is 5.0 then,
Experimental value - actual value (5.1-5.0)
Error = ------------------------------------------ = -------------- = 0.02
Actual value 5.0
Question.20) What is classification of volumetric analysis.?
Answer: Analysis can be classified as below:
- Acid base titration
- Redox titration
- Complex metric titration
- Precipitation titration
- Non eques titration
Answer: It involves the acid-base neutralization reaction in presence of water as solvent these reactions involves combination of hydrogen and hydroxide ion to form water and salt.
Question.22) What is redox titration.?
Answer: These titrations involves the reactions occurring due to transfer of electrons among reacting solutions are either oxidizing or reducing agent.
Question.23) What is complex metric titrations.?
Answer: It includes the titration of a metal ions solution with that of complexing agent to form a weakly dissociated complex substance. It usually involves titration with ethylene-diamine tetra acetic acid which is also called as EDTA.
Question.24) What is precipitation titration.?
Answer: It involves the reaction of ions to yield a precipitate. example chloride ions when combines with silver nitrate it forms silver chloride precipitates titration of silver ion with solution of chloride ion occurs in presence of nitric acid.
Cl- + AgNO3 = AgCl
Question.25) What is non-aqueous titration.?
Answer: It involves reactions between the acid and base in presence of non-equal solvent. For example of organic solvents such as benzene and chloroform.