There is no fixed  weightage of numericals in chemistry paper of  class 12 CBSE Board examination. However , there are possibilities of  getting  numerical questions on topics concernig  Chapters  1 to  4 as per NCERT chemistry book , in  short answer type - 1  ( 2 -3 marks questions )  . 

The process of electron transfer as  a result of two objects coming into frictional  contact and then separating is known as triboelectric charging.

Explanation :

The prefix tribo means ' to rub '.Triboelectric effect  is a type of contact electrification in which certain materials become electrically charged  after they come into frictional contact with a different material ( viz. rubbing glass  with fur , aplastic comb with hair. )  Thus ,   as a result of rubbing one object with another , one of the object gains electrons over its surface , and therefore becomes  negatively charged  , and simultaneously the other object loses electron from its surface ,therefore becomes positively charged . Different materials have different tendencies to  gain or lose electrons  from  their surfaces ,hence  which material becomes positive or negative depend on the relative tendencies of materials involved  to gain or lose electrons.   

Detonation is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations occur in both conventional solid and liquid explosives, as well as in reactive gases. The velocity of detonation in solid and liquid explosives is much higher than that in gaseous ones, which allows the wave system to be observed with greater detail.

Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are called alloys.

Anisole on reaction with dil sulphuric acid gives phenol and methanol.

Distillation
This is very useful for low boiling metals like zinc and mercury. The impure metal is evaporated to obtain the pure metal as distillate.

Vapour Phase Refining
The metal is converted into its volatile compound and collected elsewhere. It is then decomposed to give pure metal.
There are 2 requirements for this method:-
The metal should form a volatile compound with an available reagent,
The volatile compound should be easily decomposable, so that the recovery is easy.

An Ellingham diagram is a graph showing the temperature dependence of the stability for compounds. This analysis is usually used to evaluate the ease of reduction of metal oxides and sulfides. These diagrams were first constructed by Harold Ellingham in 1944.

In metallurgy, the Ellingham diagram is used to predict the equilibrium temperature between a metal, its oxide, and oxygen — and by extension, reactions of a metal with sulfur, nitrogen, and other non-metals. The diagrams are useful in predicting the conditions under which an ore will be reduced to its metal.

The analysis is thermodynamic in nature and ignores reaction kinetics. Thus, processes that are predicted to be favourable by the Ellingham diagram can still be slow.

In using thermodynamic principle of metallurgy, we apply the concepts of thermodynamics such as Gibb's energy (ΔG) and entropy (S) to the principles of extraction of different metals. The change in Gibbs energy, ΔG for any process at any specified temperature T, is described by the following equation :

ΔG = ΔH – TΔS

where, ΔG is Gibbs energy, ΔH is the enthalpy change and ΔS is the entropy change for the process. But the reaction will occur only when ΔG for the reaction is negative.

If the reactants and the products of the two reactions are put together in a system and the net ΔG of the two reactions is negative, then only the overall reaction will occur.

Thus the process of interpretation involves coupling of the two reactions, getting the sum of their ΔG and looking for its magnitude and sign. In this way, the thermodynamic concepts help us in understanding the theory of metallurgical transformations.

A molecule is achiral if it is superimposable on its mirror image. Most achiral molecules do have a plane of symmetry or a center of symmetry. Achiral molecules that contain a stereocenter are called meso.

It is defined as the process of separation of the individual components of a mixture based on their relative affinities towards stationary and mobile phases. Principle: The samples are subjected to flow by mobile liquid onto or through the stable stationary phase