Chemist Interview Preparation Guide
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Chemist related Frequently Asked Questions in various Chemist job Interviews by interviewer. The set of questions here ensures that you offer a perfect answer posed to you. So get preparation for your new job hunting

64 Chemist Questions and Answers:

1 :: What is Aliquot and Diluent?

Aliquot : It is a measured sub-volume of original sample
Diluent : Material with which sample is diluted

2 :: What is the difference between Molarity and Normality?

Both techniques are used to the amount of chemical present in the solution. However they are almost similar but differs in

► Molarity is used to know the total amount of molecules in a 1 litre solution
► It is expressed as moles of a compound per litre of solution

► Normality is used to know the total number of reactive units in 1 litre of solution
► It is expressed in equivalent per litre

3 :: What is Valency?

A valency is a property of a groups or atoms, equal to the number of atoms of hydrogen that the group or atom could combine with or displace it in forming compounds.

4 :: Explain the formula to calculate pH of a solution?

In order to calculate the pH of a solution you have to use the formula pH= -log [H+] or pH = -log [H3O+]

5 :: What is molality?

Molality is the number of solute that is present in 1 kg of a solvent.

6 :: Explain what is the metal used to extract copper from the solution of copper sulphate?

Fe or ferrous is the metal that is used to extract copper from the solution of copper sulphate.

7 :: What is titration?

Titration is a process to determine the molarity of a base or an acid. In this process a reaction is carried out between the known volumes of a solution with a known concentration, against the known volume of a solution with an unknown concentration.

8 :: What is the monomer of polyethene?

The monomer of polyethene is ethylene

9 :: Explain what is buffer?

A buffer is an aqueous solution which has highly stable pH. It is a blend of a weak acid and its conjugate base or vice versa. On adding small amount of base or acid to buffer, its pH hardly changes.

10 :: Explain why graphite rod is used in nuclear reactor?

Graphite rod is used in nuclear reactor to convert fast moving neutrons into thermal neutrons.

11 :: Explain how buffer works?

In buffer when hydrogen ion is added, it will neutralized by the base in buffer. Hydroxide ion will be neutralized by the acid. On the overall pH of the buffer solution, these neutralization reactions will not show much effect.

While when you select an acid as a buffer solution, try to use an acid acid that has a pH closed to your desired pH. This will help your buffer to achieve nearly equivalent amount of acid and conjugate base, so that it will enable to neutralize as much as H+ and OH -.

12 :: What is oxidation and reduction reaction?

Oxidation = When there is a loss of hydrogen or electrons, OR gain of oxygen is known as Oxidation reaction.
Reduction = When there is a gain of hydrogen or electron OR loss of oxygen is known as reduction reaction

Example of oxidation-reduction reaction is observed in human body, when an electron is transferred into the cell and oxidation of glucose take place from which we get the energy.

13 :: Explain what is mole?

Mole is the unit used to define the number of chemical substance present in a substance. It is the amount of substance which consists of the same number of chemical units as there are atoms in exactly 12 gram of pure carbon-12.

14 :: What is dextro-rotatory and levo-rotatory?

Levorotation and Dextrorotation is referred to the properties of plane polarized light, when light rotates clockwise when it approaches the observer is then known as dextro-rotation and when the light rotates anti-clockwise then it is referred as levo-rotation.

A compound which exhibits a dextro-rotation is referred as dextro-rotatory and which exhibits levo-rotation is referred as levo-rotatory.

15 :: How to calculate how many moles of glucose present in 320 mL of 5.0 M of glucose solution?

First step: Convert the volume from millilitres to litres

320 X (1 litre/1000mL) = 0.320 L solution
Second use the formula = M x V

= 5.0 moles glucose/ litre solution X 0.320 L solution

= 1.6 moles of glucose present in 320mL of solution

16 :: How many moles of HCl are present in .70 L of a .33 M HCl?

► First, remember definition of M (moles), M = moles of species / L.

0.33 M = 0.33 moles HCl / L

► Then, multiple your volume by the molar concentration:

0.33 moles HCl / L x 0.70 L = 0.231 moles HCl

It is helpful to carry the units with your calculations. That way you can check that numerators and denominators cancel to give you the units of your answer.

17 :: What is the difference between fractionation and distillation?

Both methods are used to separate the components present in the solution based on the melting points

► Distillation : This technique is used when boiling point of chemicals are different in the mixtures
► Fractionation : This technique is used when boiling point of chemicals are close to each other in the mixtures

18 :: Explain what is the IUPAC name of benzene?

The IUPAC name for Benzene is Benzene. It forms the basis for other IUPAC-named benzene derivatives like 1, 2-dimethylbenzene etc.

19 :: What is Avogadro's law?

According to Avogadro's law, at same temperature and pressure equal volume of gases contains the same number or molecules regardless of the chemical nature and physical properties.

Avogadro's number = 6.023 X 10 (-23)

20 :: How to extract ephedrine from a mineral block?

You cannot extract ephedrine or pseudo ephedrine from a mineral block. Anyone who tells you that they have done it is either mistaken or a liar.