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Classification Of Compounds

Acids Salts

Bases

Definition of an acid

Acids are the chemical substances which turn blue litmus red and

when dissolved in water, dissociate to give H+ ion

HCl + H2O ⟶ H+(aq) + Cl-(aq)

General properties of an acid

● Acids are sour in taste

● turn blue litmus red

● corrosive in nature● dissociates into H+ ions in

water

Definition of A base

Bases are the chemical substances which turn red litmus blue and

when dissolved in water, dissociate to give OH- ion

NaOH + H2O ⟶ Na+(aq) + OH-

(aq)

Bases

General properties of a base

● Bases are bitter in taste

● turn red litmus blue

● feel soapy/soft to touch● dissociate to give OH- when

dissolved in water.

Important note:

All bases are not soluble in water.

Bases which are soluble in water arecalled alkali.

Salts

How can we define a Salt

They are formed when an acid reacts with a base.

NaOH + HCl ⟶ NaCl + H2O

Indicators

● substances that are used to testwhether a substance is acidic orbasic or neutral in nature.

● They change their color whenadded to a solution containingan acidic or a basic substance.

Indicators

Onion , Vanilla Extract & Clove as Indicator

AGPRO

CHEMICAL PROPERTIES OF ACIDS AND BASES

Reaction of an Acid with Metals

Reaction of Zinc With Dil H2SO4

Acid + Metal → Salt + Hydrogen gas

Reaction of an Base with Metals

2NaOH + Zn → Na2ZnO2 + H2

Reaction of an Metal Carbonates with Acids

Reaction of Sodium Carbonate with HCl

Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)

Reaction of Sodium BiCarbonate with HCl

NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)

Reaction of an Metal Carbonates with Acids

On passing the carbon dioxide gas evolved through lime water

Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)(Lime. water)

(White precipitate)

CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)

(Soluble in water)

Reaction of Acids & Bases

Base + Acid → Salt + Water

NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Reaction of Acids & Bases

Neutralisation Reaction

The reaction between an acid and a base to give a salt and water is known

as a neutralisation reaction

Reaction of metallic Oxides with Acids

Metal oxide + Acid → Salt + Water

NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

WHAT DO ALL ACIDS AND ALL BASES HAVE IN COMMON?

● Acid or base solution in water conducts electricity.

● Acid or base, dissociates into ions when added in water.

HCl + H2O ⟶ H3O+ + Cl-

NaOH + H2O ⟶ Na+(aq) + Cl-(aq)

Can we add water Directly Into Acid ?

The process of dissolving an acid or a base in water is a highly

exothermic one.

What to do ?

If water is added to a concentrated acid, the heat generated may cause the mixture to splash out and cause

burns.

Dilution

● Mixing an acid or base with water results in decrease in the concentration of ions (H3O+/OH– ) per unit volume.

● Such a process is called dilution and the acid or the base is said to be diluted.

HOW STRONG ARE ACID OR BASE SOLUTIONS?

Strength of an acid

➢ The more will be the H+ iondissociated, the stronger will be theacid.

➢ The dissociation of H+ ion in waterdepends on the strength of the bondbetween hydrogen and othercomponent.

➢ The stronger will be the bond,the lesser will be the dissociationand vice versa.

➢ Therefore HCl is more acidic thanH2SO4

Strength of an acid

Strength of a base

➢ the more will be the OH- iondissociated, the stronger will be thebase.

➢ We can do this by making use ofa universal indicator, which is amixture of several indicators.

➢ The universal indicator showsdifferent colours at differentconcentrations of hydrogen ionsin a solution.

Strength of an acid or a base

pH Scale

pH Scale

Importance of pH in Everyday Life

● Our body works within the pH range of 7.0 to 7.8.

● Plants require a specific pH range for their healthy growth.

Importance of pH in Everyday Life

● Our stomach produces hydrochloric acid which helps in the digestion of food without harming the stomach.

● Tooth decay starts when the pH of the mouth is lower than 5.5.

● Bee-sting leaves an acid which causes pain and irritation.

● Salts having the same positive ornegative radicals are said tobelong to a family.

Family of salts

● Acidic Salts : Copper chloride● Basic Salts : Sodium bicarbonate● Neutral Salts : Sodium chloride

pH of salts

The common salt is an important rawmaterial for various materials such assodium hydroxide, baking soda,washing soda, bleaching powder andmany more.

Common salt — A raw material for chemicals

Method of preparation:

Chlor-alkali process

2NaCl + 2H2O → 2NaOH + Cl2 + H2

(aq) (l) (aq) (g) (g)

1. Sodium Hydroxide

● used for making soaps,

detergents.

● used for making papers

● used for making pesticides, PVC,

disinfectants.

Uses of Sodium Hydroxide

● Bleaching powder is representedas CaOCl2 , though the actualcomposition is quite complex.

● Ca(OH)2 + Cl2 → CaOCl2 + H2O

2. Bleaching powder

● used for bleaching cotton and

linen in the textile industry.

● as an oxidising agent in many

chemical industries

● used for disinfecting drinking

water to make it free of germs.

Uses of Bleaching powder

● The chemical name of the compound is sodium hydrogencarbonate (NaHCO3 ).

● Manufacture of Baking soda:

Solvay Process:

3. Baking Soda

● It is produced using sodiumchloride as one of the rawmaterials.

NaCl + H2O + CO2 + NH3⟶ NH4Cl + NaHCO3

3. Baking Soda

● in the making of baking powderwhich is used in making cakes.

● Sodium hydrogencarbonate is alsoan ingredient in antacids.

Uses of Baking Baking Soda

● Recrystallisation of sodiumcarbonate gives washing soda.

● It is a basic salt

4. Washing soda

● Na2CO3 + 10H2O⟶ Na2CO3.10H2O

Washing soda

Washing soda

Washing soda

● Washing soda is used in paperindustries.

● used in soap industries.● used as a cleaning agent for

domestic purposes.● for removing permanent hardness of

water.

Washing sodaUses of Washing soda

The water of crystallization meanshaving a fixed number of moleculespresent in one formula of a unit of salt.

Water of crystallisation

● The water of crystallization iscaused by forming purifiedcrystals from an aqueous solution.

● On heating these compounds thehydrated water is removed

Example:Chemical formula for hydratedcopper sulphate is CuSO4.5H2O.

Water of crystallisationWater of crystallisation

Example:

Fig. heating copper sulphate

➢ The chemical formula for gypsumis CaSO4 .2H2O

➢ It has two water molecules aswater of crystallisation.

Gypsum

Gypsum

➢ The chemical formula of plaster ofparis is CaSO4.½H2O

➢ On heating gypsum at 373 K, itloses water molecules andbecomes calcium sulphatehemihydrate (plaster of paris).

Plaster of paris

● used as plaster for supportingfractured bones in the rightposition.

● used to make sculptures andused as decorative in buildings.

● as a coating on wood and metalstructures to avoid any fireaccidents

Uses of Plaster of paris

Name the natural source of each of

the following acid

(i) Citric acid. (ii)Oxalic acid.

(iii)Lactic acid. (iv)Tartaric acid.

Home Work

Acids Bases &

Salts

One Shot

Explanation

This Session

AGPRO

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