Amarchand SinghviInternational School

Subject : Science

Class : X

Chapter : Acids, bases and salts

Topic : Salts- Family, pH of salt solutions

and Common salt ( Sodium Chloride)

Teacher : Ms. Bhavana Dubey

E-Learning Programme

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➢ Salts are formed when acids react with bases.

➢ Name of salt consists of two parts:

First part of the name is derived from the name of base.

Second part of the name comes from the name of acid.

➢Compound formed from an acid by the replacement of the hydrogen in the acid by a metal.

➢Example : HCl→ Replacement of hydrogenby Na→ NaCl.

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Hydrochloric acid→Chlorides

Sulphuric acid→Sulphides

Nitric acid→ NitratesCarbonic acid→Carbonates

Acetic acid→Acetates

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SOME IMPORTANT SALTS AND THEIR FORMULAE

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PROPERTIES OF SALTS

➢Mostly solids.

➢ Have high melting and boiling points.

➢ Usually soluble in water.

➢ Electrolytes (Solutions of salt in water conduct electricity due to presence of ions).

➢ Ionic compounds(Contains a cation→ + vely charged ion and an anion → - vely charged ion).

Example: NaCl--→Na+ + Cl –

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FAMILY OF SALTS The salts having the same positive ions or same negative ions are said to belong to a family of salts.

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pH OF SALT SOLUTIONS

➢Solution of salt in water will be neutral as salt is formed by the reaction between an acid and a base.

➢ Some salts produce acidic or basic solutions when dissolved in water.

SALT SOLUTION pH NATURE

NaCl, K2SO4 7 Neutral

NH4 Cl,Mg(NO3 )2 6 Acidic

Na2 CO3 , CH3COONa 9 Basic(Alkaline)

➢ The acidic and basic nature of some salt solutions can be explained on the basis of hydrolysis of salts.

➢ Hydrolysis means splitting up of a compound by the action of water.

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pH OF SALT SOLUTIONS

➢Sodium chloride (NaCl)Formed after the reaction between hydrochloric acid (a strong acid) and sodium hydroxide (a strong base).

➢Potassium sulphate (K2 SO4)Formed after the reaction between sulphuric acid (a strong acid) and potassium hydroxide (a strong base).

CASE-IStrong acid+ Strong base--→ Neutral solutions (pH =7)

(They do not show any action on litmus)

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CASE-IIStrong acid+ Weak base--→ Acidic solutions (pH less than 7)

➢Ammonium chloride (NH 4Cl)Formed after the reaction between hydrochloric acid (a strong acid) and ammonium hydroxide (a weak base).

➢ NH 4Cl → Dissolved in water →Hydrolysis →Forms NH4OH & HCl.➢HCl (Strong acid)→ Fully ionised→ Gives large amount of [H+ (aq)]

NH4OH (Weak base) → Slightly ionised→ Gives small amount of [OH- (aq)]

➢More H+ ions than OH- ions→ Acidic nature.

NH4 Cl (s) + H2O (l) --Hydrolysis--→ NH4 OH (aq) + HCl

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➢Sodium carbonate (Na2CO3)Formed after the reaction between carbonic acid (a weak acid) and sodium hydroxide (a strong base).

➢ Na2CO3 → Dissolved in water →Hydrolysis →Forms NaOH & H2CO3

➢H2CO3 (Weak acid)→ Slightly ionised→ Gives small amount of[H+ (aq)]

➢NaOH (Strong base) → Fully ionised→ Gives large amount of [OH- (aq)]

➢More OH- ions than H+ ions → Basic nature.

CASE-IIIWeak acid+ Strong base--→ Basic solutions (pH more than 7)

Na2 CO3 (s) + 2H2O (l) --Hydrolysis--→ 2NaOH (aq) + H2CO3

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COMMON SALT

➢ Chemical name→ Sodium chloride(NaCl)→ Neutral salt.➢ Laboratory preparation :

➢ NaCl solution formed → Evaporation → Solid sodium chloride.

➢ Occurs naturally in sea-water(dissolved form) and as rock salt (solid form).

➢ COMMON SALT FROM SEA WATER : Contains dissolved salt→Major salt present in sea-water →Evaporation → Trapping of sea-water in large, shallow pools → Slow evaporation of H2O →Common salt left behind → Impure salt as other salts are mixed with it → Send to industries.

HOW COMMON SALT IS OBTAINED

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➢ COMMON SALT FROM UNDERGROUND DEPOSITS : Rock salt→ The large crystals of common salt found in underground deposits → Usually brown due to the presence of impurities in it →Mined from the underground deposits just like coal →Was formed from the evaporated dried ancient seas thousands of years ago.

HOW COMMON SALT IS OBTAINED

Common salt obtained by evaporation of sea-water.

Rock salt obtained from underground deposits by mining.

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➢ Used as a raw material for making a large number of useful

chemicals in industry such as : sodium hydroxide, sodium

carbonate, sodium hydrogencarbonate, hydrochloric acid,

hydrogen, chlorine, sodium metal.

➢ Used in the manufacture of soap.

➢ Used as a preservative in pickles and in preserving meat and fish.

➢ Used to melt ice which collects on the roads during winter in cold

countries.

➢ Used in cooking food→ Improves the flavour of food→ Required

by our body for the movement of muscles, working of nervous s

system and production of HCl in the stomach for the digestion of

food.

USES OF COMMON SALT ( SODIUM CHLORIDE)

Note: This presentation is a part of the E-Learning Program of Amarchand

Singhvi International School and is created only for educational purpose.

Compilation & presentation : Ms. Bhavana Dubey

Web support & management : Mr. Deepak Chellani

Technical support : Mr. Shivam Gundecha

E-learning Program Co-ordination:

Mr. Prashant Chaturvedi

Produced by

Mr. Mridul Varma (Principal)

Amarchand Singhvi International School

Parekh Parisar, Ward 7A, Gandhidham – Kutch

Gujarat 370201 India