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CHAPTER-2

CHEMISTRY-ACIDS,BASES AND SALTS

The basis of chemical properties all the compared can be classified into three groups:
1
...
Bases
3
...
An indicators is a dye that changes colour
when it is put into an acid and base
...
The three most common
indicators to test for acid or base are1
...
Methyl orange
3
...

It is of two types
1
...
red litmus

An acid turns blue litmus to red
...


Litmus is a natural indicator whose natural colour is purple
...


Methyl orange- methyl orange is a synthetic indicator whose natural colour is orange
...


Phenolphthalein- phenolphthalein is a synthetic indicator whose colourless in acid
solution and gives pink colour in basic solution
OLFACTORY INDICATOR
Those substances whose smell changes in acidic or basic solution are called olfactory indicators
...
Onion and vanilla extract are olfactory indicators dove oil is
also a olfactory indicator
...
When an acid reacts with metal then a salt and
hydrogen gas are formed
...
H2SO4 + Zn → ZnSO4 + H2
In this reaction zinc displaces form sulphuric acid and this hydrogen is evolved as hydrogen gas
...
This shows hydrogen is common to all
acids
...
For e
...
– sodium
hydrogen and zinc metal is heat together them sodium zinc (8) and hydrogen gas are formed
...

HOW DO METAL CARBONATES AND METAL HYDROGEN CARBONATE REACT WITH EACH OTHER
When an acid reacts with a metal carbonate or metal hydrogen carbonate then a salt, carbon dioxide
gas and water are formed
...

NaHCO3 + HCL → NaCl + CO2 +H2O
This carbon dioxide gas reacts with lime water as follow
Ca(OH)2(lime water) + CO2 → CaCO3(PPT) + H2O
If someone is suffering from the problem of acidity after overeating, we can suggest taking baking
soda
...
This is because baking soda is sodium hydrogen carbonate which
reacts with access hydrochloric acid in the stomach an neutralises it
...
The H shells are made of calcium carbonate
...

HOW DO ACIDS AND BASES REACTS WITH EACH OTHER
When an acid reacts with a base then a salt and water are formed (Acid +BASE →SALT +WATER)

When an acid is treated with a base, the base neutralises the acid and destroy its acidity
...
So, the reaction between acid and a base top forms salt
and water is called a neutralisation reaction takes place
...
Metal oxide + acid →salt + H2O
CuO (BLACK) + HCL →CuCl2(BLUE GREEN)+H2O
The reaction between acids and metal oxide to forms salt and water is similar to the neutrilisation
reaction between an acid and a base to forms salt and water
...
So, we can say that metal oxides are basic in nature
just like metal oxides, the metal hydroxides are also basic in nature
...

REACTION OF NON- METALLIC OXIDE WITH BASE
Non-metallic oxides react with base to form CO2 and H2O
Ca (OH)2 + CO2 → CaCO3 + H20
The reaction between base and non-metallic oxides to form salt and water is similar to the
neutralisation reaction between acid and bases and non – metallic oxides is a kind of neutralisation
reaction
...

WHAT DO ALL ACIDS HAVING COMMON
All the acids contain hydrogen
...
An acid
a substance which dissociates on dissolving in water to produce hydrogen ions
...
g
...
It is the
presence of hydrogen ions in hydrochloric acid solution which makes it behave like an acid please
note that hydrogen ions do not exits as H+ ions in solutions, they attach themselves to water
molecule to form hydronium ions (H3O)
So, hydrogen ions must always be written as either H+ or as H3O
...
The acids produce
hydrogen ions only in the presence of the water does not form hydrogen ions and hence will not
show its acidic behaviour
...
Care must be taken
while mixing concentrated nitric acid or sulphuric acid with water
...
If water is added to a concentrated acid, the glass contain may
also break due to excessive local heating
...
2
...

Mixing an acid or base with water result in decrease in the concentration of ions (H2O+/OH-) per unit
volume
...


HOW STRONG ARE ACID AND BASE SOLUTIONS?
Universal Indicator:
The common indicators can tell us whether the given substance is an acid or a base
...
We can
measure the strength of an acid or a base solution by using a special type of indicator called
universal indicator
...
Universal indicator can be use either in the form of a solution or in
the form if universal indicator paper
...
In which p stands
for potinz (in German) or power and H stands for hydrogen
...

1
...
Pure water is a neutral substance
...

2
...
Whenever a solution has a pH of less than 7 it will be acidic in
nature
...
for example- a solution of pH is so much
acidic than another solution of 4 pH
...
Bases have a pH of more then 7
...
higher will be the pH, higher is the basic nature
...

Importance of pH in everyday life
The pH plays an important role in many activities of our everyday life
...
g
...
pH in our digestive system: our stomach produces hydrochloric acid of pH about 1
...
this
dilute hydrochloric acid helps in digesting our food without harming the stomach
...
antiacids are a group of mild bases which have no toxic effect on the
body
...
For e
...
- milk of
magnesia
...
pH changes as a cause of tooth decay: when we eat food containing sugar, then the bacteria
present in our mouth breakdown the sugar to form acids (lactic acid)
...
tooth decay starts when the pH of acid formed in mouth falls below
5
...
This is because then the acid becomes strong enough to attack the enamel of our teeth
and corrade it
...

Which cannot be breakdown easily but can get corraded
...

3
...
if the soil is too acidic or too basic, the plants grow badly or do not
grow at all
...
If the soil is too
acidic, then it is treated with materials like quick lime or slake lime
...

Our body works well with in a narrow pH range of 7-7
...
the aquatic animals can survive
within a narrow pH range
...
6 it is called acid rain can

lower than pH of lake water or river water to such an extent that the survival of aquatic
animals becomes difficult
...
Self defence by animal and plants: nettle is a herbaceous plant which grows in the mild
...
This is due to
the methanolic acid secreted by them, A traditional remedy is rubbing the area with the leaf
of the dock plant, which often grows beside the nettle in the mild
...
If the bee stings a person, then rubbing a mild
base like baking soda solution on the sting area of the skin gives relief
...
When a
wasp stings it injects an alkaline (base) liquid into the skin
...

Salts
Acid + base → salt + water
Strong acid + strong base → salt + water
Weak acid + weak base→ salt + water
Strong acid + weak acid →acidic salt + water
Weak acid + strong base → basic salt + water

Common salt
The common salt is a white powder which is used in preparing food, especially vegetable and pulses
...
sodium hydroxide (NaOH)
2
...
sodium hydrogen carbonate (NaHCO3) baking soda
4
...
The chemical formed of sodium hydroxide is
NaOH
...
NaOH is produced by the
electrolysis of a concentrated aqua solution of sodium chloride which is also called brine
...

Uses of sodium hydroxide
1
...

2
...

3
...

4
...

5
...

Uses of chlorine
1
...

2
...

3
...
chlorine is used as disinfectants
...
chlorine is used in CFCs
6
...

Uses of hydrogen
1
...

2
...

3
...

4
...

Uses of HCL
1
...

2
...

3
...

4
...

Bleaching powder (CaOCl2)
Calcium oxy chloride is commonly known as bleaching powder
...
It is also known as chloride of lime
...

Ca(OH)2 + Cl2 → CaOCl2 + H2O
Uses of bleaching powder
1
...

2
...

3
...

4
...

5
...

Baking soda (NaHCO3)
Sodium hydrogen carbonate is commonly known as baking soda
...
Baking soda is added for faster cooking of food such as grain
...
it is also used in soda-acid, fire extinguishers
...
sodium hydrogen carbonate is also an ingredient in antacids
...

3
...
When baking powder is heated or mixed in water, the following reactions takes place
NaHCO3 + H+ → CO2 + H2O + sodium salt of acid
...

Washing soda
Sodium carbonate is commonly known as washing soda
...

Sodium carbonate which doesn’t contain any water crystallisation is called anhidrosis sodium
carbonate
...
10H2O
USES OF WASHING SODA
1
...

2
...

3
...


4
...

CaSO4 + Na2CO3 → CaCO3 + Na2SO4
POP
Calcium sulphate hemihydrate is commonly known as plaster of Paris
...
1/2 H2O
...

Production of POP
CaSO4
...
Used in hospitals for setting fractured bones in the right position
...
used in making toys, cheap ornament, decoration materials and statues
...
used in fall celling and also for making surface smooth before painting them
...
7H2O
Na2CO3
...
2H2O

SOLID :1
...
Amorphous palter fix(X)
CaSO4
...
1/2 H2O + 1 ½ H2O
When we heat hydrated salt
...
The water molecules which form part of the structure of crystals are called water of
crystallisation
...
Every
hydrated salt has a fix member of molecules of water of crystallisation in its one formula
...
7H2O
Na2CO3
...
2H2O
It should be notice that since water of crystallisation is not free water, it doesn’t wet the salt
...
The water of crystallisation
gives the crystal of the salt their ‘shapes’ and in some cases imparts
...
7H2O is
given in colour

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