KVPY Interview Important Questions Chemistry Part 1

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1. Explain Bohr Theory model of Atom

Sol. BOHR՚s Atomic Model

Bohr՚s model is applied only on one electron species like H, , etc.

The important postulates of Bohr model of an atom are

(A) Electron revolves around the nucleus in a fixed circular orbit of definite energy. As long as the electron occupy a definite energy level, it does not radiate out energy i.e.. it does not lose or gain energy. These orbits are called stationary orbits

(B) Electron revolves only in those orbits whose angular momentum is an integral multiple of the factor (where ‘h’ is Plank՚s constant)

Where:

m = mass of the electron

v = velocity of the electron

n = number of orbit in which electron revolves

r = radius of the orbit

(C) The energy is emitted or absorbed only when the electron jumps from one energy level to another. It may jump from higher energy level to a lower level by the emission of energy and jump from lower to higher energy level by absorption of energy.

This amount of energy emitted or absorbed is given by the difference of the energies of the two energies of the two energy levels concerned

Diagram of Absorbed Energy and Emitted Energy

Q: 2. How would you derive the energy of electron orbit of Hydrogen atom? Show proper derivation

Sol. The total energy of an electron revolving in a particular orbit is

Where: P. E. = Potential energy, K. E. = Kinetic energy, T. E. = Total energy

The of an electron

And the P. E. of an electron

Hence, T. E.

We know that,

Substituting the value of in the above equation:

So, T. E.

Substituting the value of ‘r’ in the equation of T. E.

Then

Putting the value of m, e, h and π we get the expression of total energy

Q: 3. Which institute you like to join in future?

Sol. Resonance

Q: 4. Draw the shape of orbital with proper sign of orbital wave function

Sol: The wave function for has maximum amplitude along z-axis. It is zero along plane. Similarly has maximum probability of finding electron along x and y-axis.

Contour diagram for 2p-orbitals are shown in the figure given

Q: 5. What is carbine?

Sol. Carbon is a reaction intermediate in which one of the carbon is uncharged but electron deficient. It has only 6-valene . Such an intermediate is highly reactive

Example: