Electronegativity is defined as a measure of the tendency of atoms to attract electrons in a chemical bond.
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Answer : The oxidation-reduction reactions are:
I. reaction of a metal with a nonmetal
II. synthesis
III. combustion
Explanation :
Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.
Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.
Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.
I. Reaction of a metal with a nonmetal :
When sodium react with chlorine gas then it react to give sodium chloride.
In this reaction, the oxidation state of sodium changes from (0) to (+1) and shows oxidation and the oxidation state of chlorine changes from (0) to (-1) and shows reduction. So, It is an oxidation-reduction reaction.
II. Synthesis reaction :
A chemical reaction where multiple substances or reactants combine to form a single product.
When hydrogen react with oxygen then it react to give water.
In this reaction, the oxidation state of hydrogen changes from (0) to (+1) and shows oxidation and the oxidation state of oxygen changes from (0) to (-2) and shows reduction. So, It is an oxidation-reduction reaction.
III. Combustion reaction :
A chemical reaction in which a hydrocarbon reaction with the oxygen to give product as carbon dioxide and water.
When methane react with oxygen gas then it react to give carbon dioxide and water.
In this reaction, the carbon of methane gain oxygen and shows oxidation and the oxygen gas gain hydrogen and shows reduction. So, It is an oxidation-reduction reaction.
IV. Precipitation reaction :
It is defined as the reaction in which an insoluble salt formed when two aqueous solutions are combined.
The insoluble salt that settle down in the solution is known an precipitate.
It is a double displacement reaction. So, it is not an oxidation-reduction reaction.
V. Decomposition reaction :
A chemical reaction in which the the larger molecule decomposes to give two or more smaller molecules.
The oxidation state remains same on reactant and product side. So, it is not an oxidation-reduction reaction.
Answer:
Paper chromatography is a basic technique of chromatography. It consist in the separation of the mixe components using a solvent.
Explanation:
Paper chromatography is a basic technique of chromatography. It consists in the separation of the mixed components using a solvent.
Paper chromatography consists of put some dot of the mix using a glass capillary into a specialized paper, generally made of cellulose, this is called a stationary phase.
Then you put this paper into a camera of glass named, chromatography camera, where previously contain a solvent. The solvent also know as a mobile phase, the type can be defined before the test and involves a study of the kind of the mix, and the compound you want to separate.
The chromatography camera has to be closed all the time during the test, and you can't move at all because the movement of the solvent can alternate the result.
Very often, the solution of the solvent is a mix of different liquid substances with different polarities.
When the stationary phase put into the camera, the solvent starts to move up over the paper, until the separation of the compounds is observable.
the Rf is a value who relates the move of the mobile phase with the move of the distance traveled by the substance tested.
To undersant the paper chromatography, you can watch the images attached.
The first is an image of the chromatography camera.
The second one is an image of a cellulose paper after the chromatography is done. You can watch the dots who indicates the traveling of the compound across the paper.
The third one can show you the evolutions of paper chromatography, from the beginning to the end.
To calculate the Rf value you have to use the equation:
Rf = distance traveled by the substance/distance traveled by the solvent/
<u>Rf = 52mm/81mm =0.64</u>
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