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ELECTRICAL MEASURING INSTRUMENTS For the detection or measurement of electric current, potential difference, and resistance certain instruments have been devised viz. The galvanometer for the detection of small currents measurements of small currents of the order of micro amperes or mili amperes the voltmeter or potentiometer for the measurement of potential difference (and voltage) between two points of a circuit are the EMF of a source the ammeter for the measurement of large currents the wheatstone bridge the meter Bridge the post office box and the ohmmeter for the measurement of resistance. THE MOVING COIL GALVANOMETER The moving coil galvanometer is a basic electrical instrument it is used for the detection (and Measurement) of small currents. Its underlying principle is the fact that when a current flows in a rectangular coil placed in a magnetic field it experiences a magnetic torque. If it is free to rotate under a controlling torque, it rotates through an angle proportional t...
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Chemistry of Methane (CH₄) :

* In methane carbon atom has to combine with four hydrogen atoms therefore it undergoes SP3 hybridization and form four new SP3 hybrid orbital.

* The SP3 hybrid orbital are arranged in tetragonal fashion with an angle of 109.5 C

* Each SP3 hybrid orbital overlap with "S" orbital of four hydrogen atoms forming 4 sigma bonds.Thus form an orbital structure of methane.

Preparation of Methane :

* From Hydrolysis of Methyl Magnessium Iodide G.R  :

Methyl Magnessium iodide is a Grignard's reagent,it is on hydrolysis in acidic medium gives methane.

* From Reducation of IODO Methane ( Methyl Iodide) :

When iodo methane or methyl iodide is heated with molecular hydrogen in the presence of "Pb" as catalyst then it is reduced to methane.

This catalytic reduction of iodo methane is called hydrogination.
Similarly, when Iodo methane or methyl iodide is treated with Zn/HCl then it is reduced to methane by nascent hydrogen.

From Sodium Acetate CH3COONa :

When a mixture of anhydrous sodium acetate and soda lime is heated in a copper tube to form methane.

Chemical Properties of Methane :

Combustion : 

Chemical reaction in which a substance either react with free oxygen or oxygen of air with rapid release of heat and flame is called combustion.
On Combustion of methane produce CO2,H2O and large amount of heat. 

CH4 + 2O2 ----------> CO2 + 2H20 + HEAT  

Halogenation (Chlorination) :

Since methane is paraffin (less reactive) therefore it does not react with any other compound but in the presence of sunlight it react with halogen (especially chlorine) to form substitution products.This reaction is called halogenation (chlorination). 

CH4 + Cl2 ----------> HCl + CH3Cl

CH3Cl + Cl2 ----------> HCl + CH2.Cl2

CHCL3 + CL2 ----------> HCl +CCl3

CHCl3 + Cl2 ----------> HCl +CCl4 

Mechanism of Reaction :

Mechanism of chlorination of methane is a photo chemical chain mechanism,which consist of following steps.

Initiation :

The reaction starts with the formation of chlorine free radicals (Cl) .In this step chlorine molecule absorbs energy from sunlight to form chlorine free radicals.

Cl2 ( Cl-Cl ) ----------> 2Cl ( Free Radical ) 

Propagation :

In this step chlorine free radical ( Cl ) attacks methane molecule to form methyl free radical ( CH3 ). Methyl free radical ( CH3 ) than removes a chlorine atom from other chlorine molecule to form chloro-methane and chlorine free radical (Cl).

Termination :

This reaction is terminated only if any two free radicals react with each other.  

Cl + Cl ----------> Cl2

CH3 + Cl2 ----------> CH3 - Cl

CH3 + CH3 ----------> CH3 - CH3




 


           











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