CBSE CLASS 10 Chemistry Chapter-2 Acid Bases and Salt
CHAPTER - 2
Acids, Bases and Salts
All chemicals around us poses different chemical property on the basis chemical property chemical substance can be grouped into three groups.
( i ) Acids ( ii ) Bases ( iii ) Salt
Indicator
To identify acids and bases we use special type of chemical known as indicator.
Indicator are actually some chemicals which shows different color with different chemicals some indicator distinguish between acids and bases by changing their color where as some indicator by change in smell such indicator is known as alfactory indicator.
| INDICATOR | ACID | BASES |
|---|---|---|
| Litmus | Red | yellow |
| Methyl Orange | Red | Yellow |
| Phenophthlein | colorless | Pink |
| Turmeric | Yellow | Red |
| China Rose Extract | Red | Light Green |
| Red Cabbage Extract | Red | Light Green |
| Onion Extract | No Change | Odourless |
Acid
All those chemical substance which produce hydrogen ions or hydronium ion H3O+ in aquous medium is known as Acid
The word acid is derived from a letter word acidus mean sour.
It means that acids generally posses sour test.
Type of Acids
on the basis of occurence of acid are two type :-
( i ) Organic Acid
( ii) Mineral Acid
Organic Acid :
All those occuring acid which are either derived from plant and animals are known as Organic acid.
| ACID | SOURCES |
|---|---|
| Citric Acid | Lemon |
| Lactic Acid | Milk |
| Acetic Acid (CH3CooH) | Vinegar |
| Oxalic Acid | Tomato |
| Mallic Acid | Apple |
| Formic Acid (HCooH) | Ant String |
Mineral Acid :
All those acid which are prepaired by human being in laboratory by the use of mineral is known mineral acid.
Such acids are very strong in nature and also very corrosive.
| ACIDS | FORMULA |
|---|---|
| Sulphuric Acid | H2SO4 |
| Sulphuras Acid | H2SO3 |
| Nitric Acid | HNO3 |
| Nitruous Acid | HNO2 |
| Hydrochloric Acid | HCL |
| Carbonic Acid | H2CO3 |
On the basis of strength of acid are of two type :-
( i ) Strong Acid
( ii) Weak Acid
( i ) Strong Acid : Those acid which get complete ionised hence librate maximum amount of hydrogen ions known as strong acid .
( ii ) Weak Acid : Those acids which do not ionised completely hence librate less amount of hydrogen ions are known as weak acid.
All organic acids are weak in nature.
On the basis of amount of water contained acids are of two type
( i ) Dilute Acid
( ii ) Concentrated Acid
( i ) Dilute Acid : An acidic solution containing more amount of water and less amount of acid is known as dilute acid
( ii ) Concentrated Acid : Those acidic solution that contain maximum amount of acid and least possible amount of water is known as concentrated acid such acid are very corrosive in nature .
Physical property of acid :-
( i ) All acids are sour in taste.
( ii ) Acids terms blue litmus to red.
( iii ) Acids are fully soluble in water.
it aquas solution conducts electricity.
( iv ) Action with metal : Acids form matallic salt and librate hydrogen gas on reacting with metal
2HCL + 2Na --------> 2NaCl + H2
H2SO4 + Ca -------> CaSO4 + H2
Reaction with metal carbonet :
Acids forms salt carbon-di-Oxide & water on reacting with metallic carbonete
H2SO4 + CaCO3 --------> CaSO4 + CO2 + H2O
Reaction with base :
Acid shows neutralisation reation on reacting with base it forms salt and water
2HCL + Ca(OH)2 ------> CaCl2 + H2O
H2SO4 + Mg(OH)2 ---------> MgSO4 + 2H4 + 2H2O
Reaction with metallic oxide :
Acids forms salt & water on reacting with metallic oxide.
HCl + CaO --------> CaCl2 + H2O
H2SO4 + Na2O ---------> Na2SO4 + H2O
Important points of acids
All acids are corrosive in nature : it means that it remove the shiny surface of the object in which it fall some time it may cause the total spoilage of the object .
Acids not be stored in metallic contaner : Acids not be stored in metallic container because acids are corresive in nature it remove the shiney surface of metal.
Common things in all acids : All acids contains hydrogen ions it can be observed when we dissolve acids in water when acids is mixed with water then it get ionised into hydrogen ion and other negative ions .The librated hydrogen ion do not exist as hydrogen ion (H+) it get attached at with water molecule to form hydronium ion .
The acidic behavior of the solution depends upon the constration hydronium ion present in it .
In the absence of Water under unavailability of hydrogen ion acid do not show there acidic behavior.
The aquas solution of an acids conduct elecricity.
Uses of Acids :
( i ) Sulphuric acid is used in the manufacturing of fertiliser like ammonium sulphate dye, Chemical, Plastic and explosive etc.
( ii ) Sulphuric acid is used in the petroleum refining.
( iii ) Nitric acid is used for making fertiliser like ammonium.
Base
Compound having replaceble hydroxide ion are known as base. Among all base some are soluble in water soluble in water known as alkali
KOH, Mg(OH)2, Al(OH)3
Properties of Base :
( i ) Bases are bitter in test .
( ii ) They are soapy in touch .
( iii ) Aquas solution of bases conduct electricity.
( iv ) Bases turns red litmus to blue.
Reaction with metal :
when bases is allowed to react with metal it forms bimetallic salt sodium zincate and librate hydrogen gas.
2NaOH + Zn ------> Na2ZnO2 + H2
Reaction with Acid :
Bases forms salt and water on reacting with acid this reaction is known as neutralisation reaction.
NaOH + HCl ------> NaCl + H2O
2KOH + H2SO4 --------> K2SO4 + 2H2O
Ca(OH)2 + 2HNO3 ---------> Ca(NO3)2 + 2H2O
Reaction with non-metallic oxide (Acidic Oxide) :
Base forms salt and water on reacting with non-metallic oxide
Ca(OH)2 + CO2 --------> CaCO3 + H2O
Mg(OH)2 + CO2 ---------> MgCO3 + H2O
2KOH + SO3 -----------> K2SO4 + H2O
Types of Base
On the basis of strength bases are of two type :
( i ) Strong Base
( ii ) Weak Base
Strong Base : Such base get completely ionized in water and liberate maximum amount of hydroxide ion. Ex - Potassium hydroxide (KOH)
Weak Base : Those base does not ionized completely hence produce less amount of hydroxide ion Ex - Calcium hydroxide
Uses of Base :
( i ) In soap and detergent industry.
( ii ) For the manufacture of rayon.
( iii ) In paper and pulp industry.
( iv ) For white washing.
( v ) In lather industry
( vi ) For softening hard water.
PH.Scale
The ph value of solution is actually inversely proportional to the concentration of hydrogen ions it means that solution having less PH contain more hydrogen ion.
According to this scale solution having PH less than seven are acidic in nature.
Solution having ph equal to seven are neutral in nature and solution having PH more then 7 are basic in nature.
The PH value of some common solution :
| Solution | PH value (average) |
|---|---|
| Lemon Juice | 2.5 |
| Veniger | 4.0 |
| Coffee | 5.0 |
| Soft drinks | 6.0 |
| Milk | 6.5 |
| water | 7.0 |
| Egg | 7.8 |
| Tooth Pest | 8.0 |
Universal Indicator :
It is a cluster of die that shows different perception at different PH value. By this indicator we can judge the nature as well as the PH value of given solution.
Ph plays a vital role in the digestion of food and other biochemical reactions inside the human, animals body .The Ph of the gastric juice is 1-2 due to secreation of hydrochloric acid in stomach. During respiration stomach. During respiration stomach produce more acid.
Salt
It is a compound that forms by the displacement of hydrogen of an acid by a metallic atom .
HCl + NaOH -------> NaCl + H2
Naming of salt
To write the name of the salt first of all we write the name of the metal present in it then we add a suffix according to the parent acid.
like:
| Acid | Suffix |
|---|---|
| HCl | Chloride |
| H2SO4 | Sulphate |
| HNO3 | Nitrate |
| H2CO3 | Carbonate |
| CH3COOH | Acetate |
| AgNO3 | Nitrate |
| CuSO4 | Sulphate |
| CH3COONa | Acetate |
| MgCl2 | Cloride |
| CaCO3 | Calcium Carbonate |
| ZnCO3 | Zink Carbonate |
Types of salt
On the basis of PH value salt are of three types
( i ) Acidic Salt
( ii ) Basic Salt
( iii ) Neutral Salt
Acidic Salt : Such salt are formed by the reaction between strong acid with weak base.
HCl + NH4OH -----> NH4Cl + H2O
Basic Salt : Such salt are formed by the reaction between strong base with week acid.
CH3COOH + NaOH -------> CH3COONa(sodium acetate) + H2O
Neutral salt : Such salt are formed by the reaction between strong acid with strong base
HCL + NaOH ------> NaCl + H2O
Generally PH value of acid salt are nearly 6
Comman Salt
Chemical name - Sodium Chloride
Chemical formula - NaCl
Manufacture :
( i ) Inlaboratry : Inlaboratry Common salt is preapered by the reaction between hydrocloric acid with sodium hydroxide.
( ii ) Commircial method : Commercialy common salt is prepered by the slow evaporation of sea water is collected in large shallow lacks the water from such lack shallow lack the water from such lack get evaporated leaving behind salt. Now this salt is purified by the process of cristillisation after this the salt becomes edible.
Properties of Salt
( i ) It is quite cristaline.
( ii ) It is fully soluble in water its aqus solution is neautral in nature.
( iii ) Aquas solution of common salt conducts electricity.
uses of salt
( iv ) It is common ingredient of food.
( v ) it also use as preservative agent.
( vi ) Saturated aquas solution of salt is used to preserve this also.
( v ) It is used to melt the ice in cold container.
( vi ) It is also used to manufacture of various things such as shope, caustic soda, washing soda, beaking soda, etc.
( vii ) It is also used to production of hydrogen clorine and sodium metal.
Chemicals compound obtained from common salt
There are various chemical compound can be obtained from common salt some are as follow.
1. Castic Soda
Chemical name - Sodium hydroxide
Chemical formula - NaOH
Manufacture :
Castic soda is prepared in these stapes:-( i ) First of all we prepared constrated aquas solution of salt called brine solution.
( ii ) After that the brine solution is transfered in an electrolitic chambar where the solution get electrolised. on passing electric current the solution get electrolised.
( iii ) The forming cloride ions get accumulated at anode.
( iv ) From there the clorine gas as well as hydrogen gas get escaped out at last white color flacky substance remain the chamber called castic soda.
Cl- + Cl- -----> Cl2( at Anode )
H- + H- -----> H2( at Cathode )
Properties
( i ) It is white color fracky solid
( ii ) It is fully soluble in water it is basic in nature ( alkaline ).
It's aquas solution conducts electricity.
It has dirt removing capacity.
Uses of Castic Soda
( i ) For degreasing metal sheets/rod etc.
( ii ) For manufacturing soaps and detergents
( iii ) In the synthesis of artificial fibres paper etc.
2. Washing Soda
Chemical Name - Sodium Carbonate decahydrate
Chemical formula - Na2CO310H2O
Manufacture
The manufacture of washing soda is done in these steps :
( i ) First of all we preapere aquas concentrated solution of common salt known as brain solution.
( ii ) Now, Saturate it with the help of ammonia, to preapere ammonical brine.
( iii ) Now,This ammonical brine is allowed to react with carbon diaoxide gas to form solution bicarbonate and Ammonical Cloride.
NaCl + H2O + NH3 + CO2 -----> NaHCO3 + NH4Cl
( iv ) Ammonim cloride is in the form of liquid where as sodium bycarbonate is white cristile solid hence it can be precipitate out by the process of filtration.
( v ) Now we heat sodium bycarbonate to dicompose it into sodium carbonate ( sodash).
2NaHCO3 -------> Na2CO3(Sodium Carbonate) + CO2 + H2O
( vi ) Now we add ten molecule of water after cristilisation it to form washing soda
Na2CO3 + 10H2O -------> Na2CO3•10H2O
in this way washing soda is preapered
Properties
( i ) It is white cristiline power.
( ii ) It is fulley soluble in water.
( iii ) Its aquas solution is basic in nature
( iv ) It is dust removing propertise
Uses
( i ) washing soda is to prepare washing powder.
( ii ) It is also used to wash the cloth.
( iii ) It is also used to remove the hardness( due to scum ) of water.
It is also used in paper and paints industries.
3. Baking Soda
Chemical Name : Sodium Hydrogen Carbonate
Chemical Formula : NaHCO3
Maufacture
( i ) To prepare baking soda first of all we prepare concentrated aquas solution of common salt called brain solution.
( ii ) After this we saturate this solution by ammonia gas.
( iii ) Now this ammonical brain is allowed to react with CO2 to form sodium bicarbonate and ammonium clorid.
NaCl + H2O + NH3 + CO2 ------> NaHCO3 + NH4Cl
( iv ) This sodium bicarbonate can be seperated from ammonium cloride by the process of filtration.
Properties
( i ) It is in white colored cristiline powder.
( ii ) It is soluble in water.
It's aquas solution is mild basic in nature.
Uses
It can use to reduce the acidity in our stomach.
It is also used to prepare baking powder for this we mix little amount of cristiline tarteric acid.
It is also use in soda acid fire extingusher.
4. Bleaching Powder
Chemical name : Calcium Oxycloride
Chemical formula : CaOCl2
Manufacture
( i ) It is preapered by the action of dried slacked lime with clorine gas.
Ca(OH)2 + Cl2 -------> CaOCl2( Bleaching powder ) + H2O
( ii ) It is an unstable compound if it kept open for some time then all clorine gas librated leving behind calcium oxid.
Properties
( i ) It is white colored powered.
( ii ) It is partially soluble in water.
( iii ) It has a property of disinfaction, it can kill the jums present in water.
Uses
( i ) It can be used for bleaching the drinking water.
( ii ) Bleaching powder is used for disinfacting the drinking water.
( iii ) It can be used for manufacture of clorofom ( Cl2CO3 )
( iv ) It is used for making the wool unshrinkable.
( v ) It can also used as oxidising agent during redox reaction.
5. Plaster of Paris
Chemical name : Calcium Sulphate Hemihydrate
Chemical formula : CaSO4•H2O OR 2CaSO4•H2O
Manufacture
It is prepared by the controled heating of gypsum by this process gypsum get partialy dehydrated to turn into plaster of paris.
CaSO4•2H2O -------> CaSO4• ½H2O + 1½H2O
Properties
( i ) It is white colored Powder.
( ii ) It has remarkable property of setting into hard mass when get wet with water.
( iii ) It has tendancy to absorb moisture from air that leads the plaster of parish into hard mass solid due to this plaster of paris.So, we have to store plaster of paris in moisture proof bag.
Uses
( i ) It is used for making toy, idols, blackboard chalk in chemistry laboratry it is used for seating air gas.
( ii ) It also used in aurthopadic surgery for joining the fracture bone.
( iii ) Plaster of paris is also used to make heat shield around spaceship.
( iv ) It is also used to make big holl echo proof as plaster of paris prevents reflaction of sound.
6. Hydrated Salt
Salt containing water in the form of cristal is know as hydrated salt
All these salt contains water but they apper dry. As it contain water in cristiline form.
When we heat such salt we can observe water in the form of water droplet in the inner wall of testube in which the salt is being heated.
CuSO4•5H2O, FeSO4•7H2O,
MgSO4•7H2O, Na2CO3•10H2O,
CaSO4•2H2O
What happen when we heat copper sulphate strongly ?
Copper Sulphate is blue colored cristiline salt when we heat it strongly all water containt get evaporated and the color get changed from blue to white. When we add little amount of water in it copper sulphate regains it's blue color.
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