Friday 27 April 2018

Chemistry Interview Questions

1) Explain the term Aliquot and Diluent?

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

2) Explain what is molality?

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

3) Explain 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.

4) 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.

5) 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 -.

6) 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.

7) How will you 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

8) Explain 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

9) Mention 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+]
10) Explain 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
                       Normality
–       Molarity is used to know the total amount of molecules in a 1 litre solution
–       Normality is used to know the total number of reactive units in 1 litre of solution
–       It is expressed as moles of a compound per litre of solution
–       It is expressed in equivalent per litre

11) Explain 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.
12) Define 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)

13) Explain what makes a molecule into organic molecule?

In a molecule when hydrogen atom is less than the ratio of carbon atom, then such molecules are referred as an organic molecule.

14) 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.

15) Explain what is the chemical composition of fat in human body?

Fat found in human body is mainly composed of
Glycerides
Glycerides+Phospholipids
Glycolipids
Phosphoinotisides
Tocopherol

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