CLASS X - ACIDS, BASES AND SALTS

1. Acids,bases and
salts

2. ACIDS
The word acid means ‘sour’ and all acids possess these
properties. They are :-
• Soluble in water
• Corrosive
• Sour in taste
• Produce H+ (hydrogen ions)
• Conduct electricity
• pH less than 7
• Turns blue litmus red

3. EXAMPLES OF ACIDS
Vinegar (Acetic acid)
Lemon Juice (Citric acid)
Soft Drink (Carbonic acid)
Battery Acid (Sulphuric acid)
Stomach Acid (Hydrochloric acid)
Apple Juice (Malic acid)
Black Tea (Tannic acid)

4. BASES
• pH greater than 7.
• Usually forms OH-
ions in solution.
• Neutralize acids.
• Corrosive
• Bitter in taste.
• They have a soapy feel.
• Water soluble bases are called alkali.
• All alkalis are bases but all bases are not alkalis.
• Turns red litmus blue, phenolphthalein to pink and
methyl orange to yellow.

5. EXAMPLES OF BASES
Ammonia, NH3 (fertilizer, cleaning agent)
Sodium hydroxide, NaOH (cleaning agent, paper, pH regulator)
Sodium carbonate, Na2CO3 (paper, glass, detergent, toothpaste)
Sodium bicarbonate, NaHCO3 (baking soda, fire extinguisher, toothpaste)
Calcium hydroxide, or slaked lime, Ca(OH)2 (whitewashing, paper)
Calcium carbonate, CaCO3 (limestone building, blackboard chalk)
Calcium hypochlorite, Ca(ClO)2 (sanitizer, disinfectant)
Potassium hydroxide, KOH (alkaline batteries)
Aluminium oxide, Al2O3 (plastic, glass, paint)
Hydrated iron (III) oxides, Fe2O3.xH2O (rust)

6. TESTING ACID AND BASE WITH
LITMUS PAPER

7. Substances that indicate about the nature of the
given substance are known as indicators.
Types- 1. Natural indicators
2 .Synthetic indicators
Natural indicators are obtained from natural
resources like plants eg. Litmus, turmeric, petal
extracts of China Rose, Hydrangea, Red cabbage,
Geranium etc.
Synthetic indicators are chemically prepared. E.g.
Phenolphthalein, methyl orange, methyl red
INDICATORS

8. RED CABBAGE INDICATOR

9. TURMERIC INDICATOR

10. METHYL ORANGE INDICATOR

11. PHENOLPHTHALEIN
ACID BASE

12. OLFACTORY INDICATORS
Indicators that change their smell on coming in contact with an
acid or a base.

13. TRY THIS OUT !

14. Acids + Metals  Metal salt + Hydrogen gas
2HCl + Zn  ZnCl2 + H2
H2SO4 + Zn  ZnSO4 + H2
Hydrogen gas can be tested by bringing a lighted
splinter close to the mouth of the test tube,
hydrogen gas will burn with a pop sound.
REACTION OF ACIDS WITH METALS

15. REACTION OF
ACIDS WITH
METALS
Reaction of zinc
granules with
dilute sulphuric
acid and testing
hydrogen gas by
burning

16. Base + Metal  Metal salt + Hydrogen gas
Zn(s)+ NaOH(aq)  Na2ZnO2 (aq) + H2(g)
sodium hydrogen gas
zincate
REACTION OF BASES WITH METALS

17. Metal carbonate + acid  Metal salt +carbon dioxide + water
Na2CO3 (s)+2 HCl(aq)  2NaCl (aq) +H2O(l) +CO2(g)
NaHCO3 (s) +HCl(aq)  NaCl(aq) +H2O(l) +CO2 (g)
Brisk effervescence is observed due to the evolution of carbon-di-oxide
Test for CO2
Lime water turns milky on passing CO2 through it. Milkiness is due to the
formation of insoluble calcium carbonate.
Ca(OH)2 + CO2  CaCO3 +H2O
When excess of CO2 is passed, milkiness will disappear
CaCO3 + CO2 +H2O  Ca(HCO3)2 ( Calcium Bicarbonate)
REACTION OF ACIDS WITH METAL
CARBONATES & BICARBONATES

18. Acids and bases react with each other to form
salt and water. These reactions are called
neutralization reaction.
HCl(aq) +NaOH(aq)  NaCl(aq) + H2O(l)
H2SO4 (aq) + KOH (aq)  K2SO4 (aq) + H2O(l)
REACTION BETWEEN ACIDS & BASES

19. Metal oxide + Acid Metal salt + water
Metal oxides are usually basic in nature, so this
reaction is also a neutralization reaction.
CuO(s) + 2HCl(aq)  CuCl2 (aq) + H2O(l)
Black colour changes to bluish green
REACTION BETWEEN METAL
OXIDES & ACIDS

20. Non metal oxide + Base  salt + water
Non metal oxides are usually acidic in nature, so it
is also a neutralization reaction.
CO2(g) +Ca(OH) 2 (aq) CaCO3(s) + H2O(l)
REACTION OF A NON-METALLIC
OXIDE WITH BASES

21. TRY THESE OUT !
CaCO3 + 2HCl  CaCl2 + CO2 + H2O
Ca(HCO3)2 + 2HCl  CaCl2 + 2CO2 +2 H2O

22. Solution of ethanol and glucose will not conduct electricity as
they do not produce ions. Non- Electrolytes, strong
electrolytes, weak electrolytes
Acids and base produce ions in the presence of water so they
are able to conduct electricity.
WHAT IS COMMON BETWEEN ALL
ACIDS AND BASES ?

23. Acids produce H+ ions in the presence of water.
HCl H+ +Cl‾ (monoprotic acid)
4
H2SO4 2H+ + SO2- (diprotic acid)
3
HNO3  H+ + NO‾ (monoprotic acid)
Hydrogen ion does not exist alone, due to astrong
positive field it combines with a molecule ofwater
and exists as hydronium ion. H3O+ is hydrated
hydrogen ion .
H+ + H2O  H3O+ ( Hydronium ion)
IONS PRODUCED BY ACIDS

24. Dry HCl does not show acidic properties as HCl does not dissociate into
ions in the absence of water.

25. Bases produce OH- ions in the presence of water.
E.g NaOH  Na+ + OH-
KOH  K+ +OH-
Ca(OH)2  Ca2+ +2OH-
4
NH4OH  NH + + OH-
All bases are not soluble in water. Bases that are
water soluble are called alkalis
During a neutralization reaction,
H+ + OH-  H2O
(from acid) (from base)
IONS PRODUCED BY BASES

26. Acids and bases are highly corrosive so it should be
handled carefully.
During dilution water should not be added to acid
rather acid should be added to water with constant
stirring because dissolution of acids is a highly
exothermic process. The heat evolved may cause
the mixture to splash and cause burn injuries.
Temporary heating may also cause the apparatus to
break.
During dilution concentration of H+ ions decreases
per unit volume, so the strength of acids will also
decrease.
DILUTION OF ACIDS

27. Strong acids dissociate completely in the solution. It will
generate large number of hydrogen ions.
Eg. HCl, H2SO4, HNO3, HClO4
Weak acids dissociate partially in the solution. It will
generate lesser number of hydrogen ions.
Eg. CH3COOH  (CH3COO- ) + H+, HCOOH, HCN
Strong bases dissociate completely in the solution. It will
generate large number of hydroxide ions.
Eg. NaOH, KOH, Ca(OH)2,Mg(OH)2
Weak bases dissociate partially in the solution. It will
generate lesser number of hydroxide ions
Eg. NH4OH
STRONG AND WEAK ELECTROLYTES

28. TRY THESE OUT !

29. UNIVERSAL INDICATOR
This indicator is a mixture of many other indicators. The
colour shown by this indicator can be matched against a
pH Scale.
pH = - log [H+]
Potent of hydrogen ion
|---------Acids----------------|Neutral|----------- Bases---------|

30. pH SCALE
Acidic solutions have greater concentration of hydrogen ions.
Basic solutions have greater concentration of hydroxide ions.
pH value less than 7 – Acidic
pH value 7- Neutral
pH value more than 7 - Basic

31. • Plants need optimum pH of the soil for proper growth
Living organisms can survive in a very narrow range of pH . Due to acid
rain when pH of the water resources decreases , it becomes very difficult
for the survival of aquatic organisms.
• Our stomach produces hydrochloric acid for the digestion of food. Due to
indigestion stomach produces excess of acid which causes acidity i.e
pain and irritation. By taking Antacids, the excess acid in the stomach
gets neutralized . Milk of magnesia , baking soda solution can be taken
for this purpose.
• Tooth decay starts when pH of the mouth is less than 5.5. Due to
bacterial action on food remains between the teeth, acids are produced.
These acids will lead to cavities on reaction with enamel (calcium
phosphate). So toothpastes are generally basic in nature which helps to
neutralize the excess acid present in the mouth.
IMPORTANCE OF pH IN
EVERYDAY LIFE

32. IMPORTANCE OF pH IN EVERYDAY LIFE
 Bee stings/stings by red ants inject methanoic acid into our body
causing pain and irritation. By applying basic substances like baking
soda solution or tooth paste one can get relief from pain as it will
neutralize the effect of acid.
 Stinging hair of nettle leaves also injects methanoic acid. By
applying the extract of dock plants, one can get relief from pain.
Weak acids dissociate partially in the solution. It will generate lesser
number of hydrogen ions.

33. Substance Acid
Tamarind Tartaric acid
Lemon, Orange Citric acid
Tomato ,Guava Oxalic acid
curd Lactic acid
Ant sting Methanoic acid
Nettle leaf sting Methanoic acid
Vinegar Acetic acid
apple Malic acid
SOME NATURALLY OCCURING ACIDS

34. TRY THESE OUT !

35. What are the formulae of the following salts?
Potassium sulphate, sodium sulphate,calcium
sulphate, magnesium sulphate, copper sulphate,
sodium chloride, sodium nitrate, sodium carbonate,
ammonium chloride
Identify the acid and the base from which these salts
have been derived.
• NaCl ----- ?
• NH4Cl ----- ?
SALTS

36. pH OF SALT
 Strong acid + Strong base – Neutral salt, pH value is 7
E.g. NaCl – NaOH + HCl
 Strong acid + weak base – Acidic salt ,pH value is less
than 7
E.g. NH4Cl- NH4OH + HCl
 Strong base + weak acid – Basic salt, pH value is more
than 7
E.g. CH3COONa – CH3COOH + NaOH
Sodium acetate

37. Chemical formula: NaOH
Chemical name: Sodium hydroxide
Common name : Caustic soda
Preparation: It is prepared by passing electricity through
brine ( concentrated NaCl solution)
2NaCl +2H2O  2NaOH + H2 +Cl2
The above process is also known as Chlor- alkali process
Chlorine gas is liberated at anode and hydrogen gas at cathode
Uses: NaOH: 1. For making soap, detergents 2. degreasing metals
3. paper making 4. artificial fibers
H2: For making margarines, as a fuel, for making ammonia for
fertilizers
Cl2: as a disinfectant, water treatment plants, for making PVC, CFC,
pesticides
SODIUM HYDROXIDE

38. CHLOR- ALKALI PROCESS

39. Chemical formula: CaOCl2
Chemical name: Calcium oxy chloride
Preparation: By carrying out reaction between
slaked lime and chlorine gas.
Ca(OH)2 + Cl2  CaOCl2 + H2O
Uses:1. For bleaching cotton , linen in textile
industry.
2. As an oxidation agent in chemical industries
3. For disinfecting water
BLEACHING POWDER

40. Chemical formula: NaHCO3
Chemical name: Sodium bicarbonate
Preparation: Solvay’s process
Raw materials required: NaCl, CO2, H2O, NH3
NaCl + CO2+H2O+ NH3  NaHCO3 + NH4Cl
Uses: 1. Baking soda is used to prepare baking powder. Baking powder
is a mixture of baking soda and tartaric acid. Tartaric acid neutralizes
the effect of sodium carbonate formed during the reaction.
2. It is used for making cakes and breads soft and spongy
2NaHCO3( heat) Na2CO3 + H2O + CO2
CO2 released makes the cake soft and fluffy
3. Being basic in nature , baking soda solution is used as an antacid.
It neutralizes the excess present in the stomach.
4. For making soda acid fire extinguisher
BAKING SODA

41. Chemical formula: Na2CO3.10H2O
Chemical name : Sodium carbonate decahydrate
Preparation: Sodium hydrogen carbonate obtained by
Solvay’s process when heated gives sodium carbonate.
Recrystallisation of sodium carbonate gives washing soda.
Na2CO3 + 10 H2O  Na2CO3.10H2O
Uses:1. Used in glass, soap and paper industry.
2. For removing permanent hardness of water.
(Permanent hardness cannot be removed by boiling)
3. As a cleansing agent for domestic purpose
4. For making Borax.
WASHING SODA

42. Chemical formula: CaSO4.1/2 H2O
Chemical name: Calcium sulphate hemihydrate
Preparation: By controlled heating of Gypsum (100 C)
CaSO4.2H2O  CaSO4.1/2 H2O + 3/2H2O
Gypsum (100 C) P.O.P
Uses: 1. For making toys, decorative items, false ceiling
2. For supporting fractured bones.
3.For making uneven surfaces smooth during painting of walls.
On adding water P.O.P combines with water and forms gypsum again.
CaSO4.1/2 H2O + 3/2H2O  CaSO4.2H2O
PLASTER OF PARIS

43. Water of crystallization is the fixed number of water molecules present
in one formula unit of a salt.
E.g. CuSO4.5H2O, FeSO4.7H2O, Na2CO3.10H2O, CaSO4.1/2H2O
Upon heating blue coloured crystals of copper sulphate , it turns
white due to loss of water of crystallization.
WATER OF CRYSTALLISATION

44. TRY THESE OUT !