Question Paper

AHSEC (Assam higher secondary education council), HS final exam question paper 2016

HS final exam question paper 2016

AHSEC (Assam higher secondary education council), HS final exam question paper 2016

AHSEC (Assam higher secondary education council) final exam question paper 2016/ HS final exam question paper 2016/ class 12 Assam HS final exam question paper of the year 2016 are available on this site. The question papers are available in the pdf format. The questions papers of the subjects are physics, chemistry, mathematics, biology and English. And also some important topics of the paper of physics, chemistry, mathematics, biology and English

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Mathematics

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Physics

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Chemistry

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Biology

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English

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English

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Assamese

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Some important topics of chemistry

The conductivity of solid:

Based on the conducting power solids are divided into 3 types –
1) Conductor :
Conductivity range is 10^4 to 10^7 ohm^-1m^-1
2) Insulator:
Conductivity range is 10^-20 to 10^-10 ohm^-1m^-1
3)Semi-conductor:
Conductivity range is 10^-6 to 10^4 ohm^-1m^-1

The conducting capacity is based on the energy differences between conduction band and valance band. In solid the molecular orbitals are so closed in energy to form band. There are two types of band-

1)Valances band or occupied band.
2)Conduction band or unoccupied band or empty band.

In case of good conductor the valance band and the conduction band are very closed to each other or overlapping with each other. Therefore electron can easily jump from valance band to conduction band. In case of insulator valances band and conduction band are far apart from each other that electrons can not jump from valance to conduction band. The gap between valance band and conduction band is called forbidden zone.
On the other hand in case of semiconductor, the energy gap between valance band and conduction band is intermediate to that between conductor or insulator. Therefore very less number of an electron can jump from valance band to conduction band.

Colloid:

The colloid is a heterogeneous system in which one substance is dispersed as very fine particles in another substance. The substance which is a dispersed phase and the substance on the surface of which dispersion take place is called depression medium. The colloidal solution depends on the particles sizes of the depressed phase. The colloidal range is 1nm to 1000nm.

Classification of colloid based on the interaction between dispersed phase and dispersion medium :

On this basis they are divided into 2 types –

1) Lyophilic colloid :
When the interaction between dispersed phase and the dispersion medium is very strong the resulting colloid is called lyophilic colloid.
eg: Starch, gel, gum etc are a lyophilic colloid. An important character of lyophilic colloid is that when dispersed phase is separated from dispersion medium, the colloid can be reconstituted by simply mixing with the dispersion medium i.e why it is also called reversible colloid.
2) Lyophobic colloid :
When the interaction between dispersed phase and the dispersion medium is very weak the colloid is called lyophobic colloid. They cannot be prepared by simply mixing dispersed phase and dispersion medium. They can be prepared by special technique but when dispersed phase and dispersion medium are separated from each other, the sol cannot be reconstituted by simple mixing.
eg: Sulphide sol, gold sol, silver sol. It is also called irreversible sole

Classification of colloid based on the size of particle:

1) Multimolecular colloid:
When colloids are formed by combining or association of a large number of atoms of a molecule to form a particle having the size in the colloidal range is called Multimolecular colloid.
eg: gold sol, silver sol.
2) Macromolecular colloid:
In this colloid, the particles are large molecules like protein, polymers, enzyme etc. These molecules have the size in the colloidal range.
3) Associated colloid:
There is some substance which at low concentration behaves as normal strong electrolytes but at higher concentration exhibit colloidal behavior due to the formation of aggregates. The aggregate particles are called micelles. This is also known as Associated colloids. The minimum concentration at which the formation of micelles take place is called critical micelles
concentration (CMC). The formation of micelles takes place only above a particular temperature known as Kraft temperature.
eg: Soap and detergent.

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