Class 9th English Medium Notes of Chemistry chapter 6, 7 and 8

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Class 9th English Medium Notes of Chemistry chapters 6, 7 and 8: Here I Am Give You Very Important Notes of Chemistry chapters 6, 7 and 8 For Class 9th. I hope I’ts Help You Exam.

Unit 6


The solution may be a homogeneous mixture of two or more substances.

The aqueous solution is made by dissolving substances in water.

The component which is lesser in quantity is named solute and therefore the component in greater quantity is named solvent.

A solution containing less amount of solute than that’s required to saturate it at a given temperature is named unsaturated solution.

A solution that’s more concentrated than that of a saturated solution is named as a supersaturated solution at that specific temperature.

The solution could also be dilute or concentrated depending upon the number of dissolved solutes in a solution.

The concentration of solutions is expressed at least w/w, % w/v, % v/w and a couple of v/v.

The practical unit of concentration is molarity. it’s the number of moles of solute dissolved in one dm3 of solution.

Solubility is defined because the number of grams of the solute dissolved in 100 g of solvent to organize a saturated solution at a given temperature. It depends upon solute-solvent interactions and temperature.

Colloidal solutions are false solutions and within these solutions, particles are bigger than in the true solutions.

Unit 7

Oxidation is the addition of oxygen or removal of hydrogen or loss of electrons by a component and as a result oxidation state increases.

The reduction is the addition of hydrogen or removal of oxygen or gain of electrons by a component and as a result oxidation state decreases.

The oxidation number is that the apparent charge on an atom. it’s going to be positive or negative.

Oxidizing agents are the species that oxidize the opposite element and reduce themselves. Non-metals are oxidizing agents.

Reducing agents are species that reduce the opposite elements and oxidize themselves. Metals are reducing agents.

Chemical reactions during which the oxidation number of species change are termed as a redox reaction. A redox reaction involves oxidation and reduction processes happening simultaneously.

Redox reactions either happen spontaneously and produce energy or electricity is employed to drive the reaction.

The process during which electricity is employed for the decomposition of a compound is named electrolysis. It takes place in electrolytic cells like Downs cell and Nelson’s cell.

Galvanic cells are those during which spontaneous reactions happen and generate current. they’re also called voltaic cells.

Sodium metal is manufactured from fused common salt within the Downs cell.

NaOH is manufactured from brine in Nelson’s cell.

Corrosion is a slow and continuous erosion of a metal by the encompassing medium. the foremost common example of corrosion is rusting of iron.

The rusting principle is an electrochemical redox reaction, during which iron behaves as an anode. Iron is oxidized to make rust Fe2O3. nH2O.

Corrosion is often prevented by many methods. the foremost important is electroplating.

Electroplating is depositing of 1 metal over the opposite by means of electrolysis.

Iron is often electroplated by tin, zinc, silver or chromium.

Unit 8

The formation of cations of alkali and alkaline-earth metal metals is thanks to their electropositive behavior.

The chemical reactivity of alkali and alkaline-earth metal metals is sort of different.

Calcium and magnesium are less reactive than sodium.

Halogens form very stable compounds with alkali metals.

Mercury and gold exist in free elemental form in nature.

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