Interview Question on Wet Chemistry
1)What is LOD test?
Ans: The 'Loss on Drying' Test is designed to measure the amount of water and volatile matters in a sample when the sample is dried under specified conditions.
2)What do you mean by sulphated ash?
Ans: The sulfated ash test utilizes a procedure to measure the amount of residual substance not volatilized from a sample when the sample is ignited in the presence of sulfuric acid. The test is usually used for determining the content of inorganic impurities in an organic substance.
3) What is the meaning of loss on drying?
Ans: Loss on drying is a widely used test method to determine the moisture content of a sample, although occasionally it may refer to the loss of any volatile matter from the sample. The loss in drying does not usually refer to molecularly bound water or water of crystallization.
4) What is a vacuum drying oven?
Ans: A vacuum drying oven is most often used for delicate drying processes, such as drying tiny parts or removing flammable solvents. The low-pressure environment also minimizes oxidation during drying. A standard vacuum oven can operate at temperatures as high as 200ºC to 250ºC.
5) What is the residue on ignition?
The Residue on Ignition / Sulfated Ash test utilizes a procedure to measure the amount of residual substance not volatilized from a sample when the sample is ignited in the presence of sulfuric acid according to the procedure
6) What is vacuum drying?
Ans: Vacuum drying can be a useful tool for solid products that are heat-sensitive. Here are some guidelines for the selection and use of various types of vacuum dryers. Drying is an essential unit operation in a variety of chemical process industries (CPI) sectors.
7) What do you mean by optimum moisture content?
Ans: The Optimum Water Content of soil is the water content at which a maximum dry unit weight can be achieved after a given compaction effort. A max dry unit weight would have no voids in the sample.
8) What is the meaning of ash content?
Ans: Ash content refers to the mineral content of a flour, and is determined by burning a given quantity of flour under prescribed conditions and measuring the residue.
9) What is the difference between water content and LOD?
Ans: The difference between content and LOD are,
[1] Water content- the amount of water present in the analyte in any form(including hydrated molecule)
[2] Loss on the Drying-The amount of volatile substances present in the analyte (all volatile solvents present including water)
10) What is the difference between LOD under drying and LOD under vacuum?
Ans: Both are used for the same purpose of determining the presence of water and organic solvents present in the sample by vaporizing them
[1] LOD under drying: In this, we dry the sample at a temperature of more than the water boiling range.Generally, we use 105ºC because of water boiling point is 100ºC and most of the solvents have boiling point lower than 100ºC.This method is suitable only when, our sample has melting point is more than 100ºC. If our sample having melting point less than 100ºC then we cannot determine the water or any solvent having the boiling point less than the drying temperature.
11) What is Primary standard?
The requirement of Primary standards:
- It should be available in pure form or in a state of known purity. In general, the amount of impurity should not exceed 0.01-0.02% and it should be possible to test for impurity by qualitative tests by known sensitivity.
- The substance should be easy to dry and should not be hygroscopic that it takes up water during weighing and should not efflorescence that it spontaneously loses water molecule to the atmosphere. It should not lose on exposure to air.
- The primary standard should have high equivalent weight in order to minimize the errors in weighing.
- It is preferable to the acids or base be strong that is highly dissociated. However, week acid or week base may be employed as a primary standard with no great disadvantages.
- It should be stable, non-toxic and eco-friendly (environmentally)
12) What is Secondary standard?
Ans: A solution standardized by titrating with the primary standard itself is called as a secondary standard.
Ex. NaOH, HCl, EDTA
1)What is LOD test?
Ans: The 'Loss on Drying' Test is designed to measure the amount of water and volatile matters in a sample when the sample is dried under specified conditions.
2)What do you mean by sulphated ash?
Ans: The sulfated ash test utilizes a procedure to measure the amount of residual substance not volatilized from a sample when the sample is ignited in the presence of sulfuric acid. The test is usually used for determining the content of inorganic impurities in an organic substance.
3) What is the meaning of loss on drying?
Ans: Loss on drying is a widely used test method to determine the moisture content of a sample, although occasionally it may refer to the loss of any volatile matter from the sample. The loss in drying does not usually refer to molecularly bound water or water of crystallization.
4) What is a vacuum drying oven?
Ans: A vacuum drying oven is most often used for delicate drying processes, such as drying tiny parts or removing flammable solvents. The low-pressure environment also minimizes oxidation during drying. A standard vacuum oven can operate at temperatures as high as 200ºC to 250ºC.
5) What is the residue on ignition?
The Residue on Ignition / Sulfated Ash test utilizes a procedure to measure the amount of residual substance not volatilized from a sample when the sample is ignited in the presence of sulfuric acid according to the procedure
6) What is vacuum drying?
Ans: Vacuum drying can be a useful tool for solid products that are heat-sensitive. Here are some guidelines for the selection and use of various types of vacuum dryers. Drying is an essential unit operation in a variety of chemical process industries (CPI) sectors.
7) What do you mean by optimum moisture content?
Ans: The Optimum Water Content of soil is the water content at which a maximum dry unit weight can be achieved after a given compaction effort. A max dry unit weight would have no voids in the sample.
8) What is the meaning of ash content?
Ans: Ash content refers to the mineral content of a flour, and is determined by burning a given quantity of flour under prescribed conditions and measuring the residue.
9) What is the difference between water content and LOD?
Ans: The difference between content and LOD are,
[1] Water content- the amount of water present in the analyte in any form(including hydrated molecule)
[2] Loss on the Drying-The amount of volatile substances present in the analyte (all volatile solvents present including water)
10) What is the difference between LOD under drying and LOD under vacuum?
Ans: Both are used for the same purpose of determining the presence of water and organic solvents present in the sample by vaporizing them
[1] LOD under drying: In this, we dry the sample at a temperature of more than the water boiling range.Generally, we use 105ºC because of water boiling point is 100ºC and most of the solvents have boiling point lower than 100ºC.This method is suitable only when, our sample has melting point is more than 100ºC. If our sample having melting point less than 100ºC then we cannot determine the water or any solvent having the boiling point less than the drying temperature.
[2] LOD under vacuum: If our sample has lower melting point range (less than 100ºC ) like 70-58ºC etc...we cannot vaporize the water or any other solvent more than drying temperature in this case we use somewhat less temperature than the sample for drying by applying proper vacuum to, absorbs the water or solvents present in the sample.
Note: The main difference of both the methods is when sample have the high melting range (more than 100ºC) we can determine LOD by drying and when sample has the low melting range (less than 100ºC) we can use LOD by drying under vacuum.
11) What is Primary standard?
Ex. Na2CO3, PHP(Potassium hydrogen phthalate)
The requirement of Primary standards:
- It should be available in pure form or in a state of known purity. In general, the amount of impurity should not exceed 0.01-0.02% and it should be possible to test for impurity by qualitative tests by known sensitivity.
- The substance should be easy to dry and should not be hygroscopic that it takes up water during weighing and should not efflorescence that it spontaneously loses water molecule to the atmosphere. It should not lose on exposure to air.
- The primary standard should have high equivalent weight in order to minimize the errors in weighing.
- It is preferable to the acids or base be strong that is highly dissociated. However, week acid or week base may be employed as a primary standard with no great disadvantages.
- It should be stable, non-toxic and eco-friendly (environmentally)
Ans: A solution standardized by titrating with the primary standard itself is called as a secondary standard.
Ex. NaOH, HCl, EDTA
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