Acid, Base and Salt. Science Plus one NIOS

1. ACIDS, BASES & SALTS

2. ACID
❏ Latin term ‘accre’ means sour
❏ Used by Robert Boyle in 17th century
❏ It’s a substance which release hydrogen ions (H+) when dissolved in water.
❏ (H+) does not exist alone, it combines with water molecule (H2O) and forms
(H3O+) (Hydronium ion)
Eg:- HCl — H++Cl-

3. BASES
● The substances which hydroxide ions (OH-) when dissolved in water.
● Bases soluble in water called Alkalis
Eg: NaOH, KOH
➔ Neutralization is the chemical reaction in which acid and base quantitatively
react together to form a salt and water as products.

4. Properties
ACID
● Taste sour
● Feel like water
● Corrosive to metals
● Change blue litmus to red
● React with metals and forms H2 & Salt
● React with Base to form water and salt
(Neutralization)
● Conduct electricity when dissolved in
water
● Colorless in phenolphthalein.
BASE
● Taste bitter
● Feel soapy
● Non- reactive with metals
● React with acid to form water and salt
(Neutralization)
● Change red litmus to blue
● Pink color in phenolphthalein
● Conducts electricity when dissolved in
water

5. Properties
DILUTE ACID
● Decrease hydronium ion concentration
● Highly exothermic reaction
DILUTE BASE
● Decrease hydroxide concentration
● Exothermic reaction

6. Strength of Acids/ Bases
● Strong acid releases more H+ ions like
HCL
● Weak acid releases less H+ ions like acetic
acid
● Strong base releases more OH- ions like
NaOH
● Weak base releases less OH- ions like
Ammonium Hydroxide (NH4OH)

7. Common acids
● Vinegar- Acetic acid
● Tomato- Oxalic acid
● Orange, lemon- Citric acid, ascorbic acid
● Tamarind, grapes- Tartaric acid
● Curd- Lactic acid

8. Mineral & Organic acids
➔ Mineral acids are those acids that are man-made and derived from one or
more inorganic compounds.
➔ Organic acids are the acids found naturally in plants and animals. They are
weak acids and do not dissociate completely in water.

9. Indicators

10. Indicators
● Substances that tell us whether a substance is acidic or basic by change in
color, smell etc…
Types of indicators:
Olfactory indicator: Substances that changes its odour in acidic or basic
media like Vanilla, Onion etc…
Natural indicator: turmeric, Litmus (Obtained from lichen, hibiscus etc..)
Synthetic indicator: Methyl Orange, Phenolphthalein.

11. Indicators
Indicator Natural color Acids Bases
Red litmus Red Remains red Turns Blue
Blue litmus Blue Turns red Remains blue
Phenolphthalein Colorless Colorless Pink
Methyl Orange Reddish Orange Red Yellow

12. Phenolphthalein test

13. Acid

14. Properties of Acid
1. Taste
2. Action on indicators
3. Conduction of electricity and dissociation of acids
4. Reaction of acids with metals
5. Reaction with metal carbonates and hydrogen carbonates
6. Reaction with metal oxides
7. Reaction with bases
8. Corrosive nature

15. 3. Conduction of electricity and dissociation of acids
Dissociation: Process of producing ions which help conducting electricity when
acid dissolved in water.
H+ + H2O H3O+ H+(aq)
Hydrogen ion Hydronium ion

16. 3.1 Strong & weak acids
Strong acid
Acid which completely dissociate in water are
called strong acids.
Eg:- Nitric acid
HNO3 H+ + NO3
Strong acids :- Mineral acids like Hydrochloric
acid (HCl), Hydrobromic acid (HBr), Hydroiodic
acid (HI) etc..
Weak acid
Acid which partially dissociate in water are
called weak acids.
HF ⇌ H+ + F-
Weak acids:- Organic acids like citric acid,
Oxalic acid etc..

17. 4 Reaction of acid with metal
Acid + Metal Salt + Hydrogen gas
Eg:- Zn + H2SO4 ZnSO4 + H2
Zinc
metal Diluted sulphuric acid Zinc sulphate salt Hydrogen gas

18. 5. Reaction of acid with metal carbonate & Hydrogen Carbonate
Acid + Metal Carbonate Salt + CO2+ H2O
Eg:- 2HCl + MgCO3 MgCl2 +CO2 + H2O
Acid + Hydrogen Carbonate Salt + CO2+ H2O
Eg:- HCl + Na2CO3 NaCl + H2O + CO2

19. 6. Reaction of acid with metal oxides
Acid + Metal Oxide Salt + Water
Eg:- CuO + 2HCl CuCl2 + H2O
Copper Oxide Diluted Hydrochloric
acid Copper Chloride
Water

20. 7. Reaction of acid with bases
Acid + Base Salt + Water
Eg:- HCl + NaOH NaCl + H2O
Hydrochloric acid Sodium Hydroxide Sodium Chloride
Water

21. Base

22. Properties of Base
1. Taste and touch
2. Action on indicators
3. Conduction of electricity & dissociation of ions
4. Reaction with metals
5. Reaction with non-metal oxides
6. Reaction with acids

23. Conduction of electricity & dissociation of ions
★ The bases which are soluble in water and give OH- ions in their aqueous
solution are called alkalis.

24. 3.1 Strong & weak bases
Strong base
Base which completely dissociate in water and
form OH- are called strong bases.
Eg:- KOH K+ + OH-
Strong bases :- Lithium hydroxide (LiOH),
Sodium hydroxide (NaOH), Rubidium hydroxide
(RbOH) etc
Weak base
bases which seldomly produce OH- ions when
dissolved in water are called weak bases.
NH3+ H2O ⇌ NH4
+ + OH-
Weak bases: Ammonium hydroxide(NH4OH),
Copper hydroxide (Cu(OH)2)

25. Reaction of base with metal
Metal + Base Salt + Hydrogen gas
Eg:- 2NaOH + Zn Na2ZnO2 + H2
Sodium Hydroxide
Zinc Metal Sodium zincate
Hydrogen

26. Reaction of base with non-metal Oxides
Non-metal Oxide + Base Salt + Water
Eg:- Ca(OH)2 + CO2 CaCO3 + H2O
Calcium Hydroxide
Carbon dioxide Calcium carbonate
Water

27. Reaction of base with acid
Acid + Base Salt + Water (Neutralization)
Eg:- HCl + KOH KCl + H2O
➢ Neutralization is the process in which acid react with base each other to
produce salt and water.
➢ Salt is obtained when hydrogen of acids is replaced by the metal.
Eg:- HCl NaCl, H2SO4 Na2SO4
Common Salt:- NaCl is Obtained from sea

28. Fact Checking
➔ Metallic Oxides are Basic Oxides:
Because metallic oxides react with acids to give salt and water, similar to the
reaction of a base with an acid
➔ Non-metallic oxides are Acidic oxides:
Because non-metallic oxides react with bases to give salt and water, similar
to the reaction of an acid with base.

29. Role of water in dissociation
➔ Most of the acids and bases have no dissociation (furnishing H+ and OH-)
without water.
➔ Dissociation process is highly exothermic.

30. Self dissociation of water
➔ Dissociation of water itself is extremely small and only about 2 out of every billion water
molecules are dissociated in 25oC.
➔ H2O ⇌ H+ +OH-
➔ H+= OH- = 1.0 x 10-7
➔ Pure water or ionic product of water is H+= OH- It’s symbolized as Kw (Ionic Constant
product of water). So we conclude that:
Kw = [H+] [OH-] ie: Kw = (1.0 x 10-7) x (1.0 x 10-7)
Kw = 1.0 x 10-14

31. Solutions
❏ Neutral Solution: H+= OH- = 1.0 x10-7 mol L-1
❏ Acidic Solution: H+> OH- Or [H+] > 1.0 x10-7 mol L-1
❏ Basic Solution: H+< OH- or [H+] < 1.0 x10-7 mol L-1

32. pH Scale

34. pH and its importance
➔ pH means the power of hydrogen
➔ It was denoted by Danish biochemist Soren Sorensen in 1909.
pH= log 1/[H+]
➔ Acid rain is 5.6 pH

35. log and value
1. 0
2. 0.3
3. 0.5
4. 0.6
5. 0.7
6. 0.8
7. 0.85
8. 0.9
9. 0.95
10. 1

36. pH and its importance
➔ pH= -log [H+]
➔ pOH= -log [OH-]
➔ pKa= -log Ka
➔ pKb= -log Kb
➔ pKw= -log Kw

37. pH and its importance
➔ pKw = 14
➔ pKa + pKb = pKw = 14
➔ pH + pOH= 14
-log a x 10-x = x- log a

38. Examples
Question: [H+] = 5x 10-3 , then what is pH?
Answer: pH= -log [H+]
-log a x 10-x = x- log a
= -log 5x 10-3
= 3- log 5
3-0.7= 2.3
Question: [H+] = 0.0002, then what is pH?
Answer: = 2x 10-4
Then,
pH= -log [H+]
pH = -log 2x 10-4
= 4- log 2
= 4 - 0.3
= 3.7

39. Comprehensive checking
Question: 0.02 HCl
[H+] = 0.02x 1
[H+] = 2 x 10-2
pH= -log 2 x 10-2
= 2- log 2
=1.7
Question: 0.02 H2SO4
[H+] = 0.02x 2
[H+]= 4 x 10-2
pH= -log 4 x 10-2
2- log 4 = 2- 0.6
= 1.4

40. Common acids and bases
Common acids pH Value Common Bases pH Value
HCl 0 Blood Plasma 7.4
Stomach acid 1 Egg white 8
Lemon Juice 2 Sea water 8
Vinegar 3 Baking soda 9
Oranges 3.5 Antacids 10
Soda, Grapes 4 Ammonia water 11
Sour Milk 4.5 Lime water 12
Fresh Milk 5 Drain cleaner 13
Human Saliva 6-8 Caustic soda 14
Pure water 7

41. Determination of pH
Using pH Paper or Universal indicator

42. Use of pH in everyday life
➔ pH in humans and animals: Biochemical reactions in our body are narrow are
in narrow pH range of 7.0 -7.8. Even small change in it disturbs this process.
➔ Acid rain: if rain water falls below pH 5.6 it’s called acid rain.
➔ pH in plants: plants have a healthy growth when a specific pH range is
maintained.
➔ In digestive system: Our stomach produce hydrochloric acid which helps
digestion of food.
➔ Self defence of animals and plants: Bee sting causes severe pain and burning
sensation.it’s due to methanoic acid. Use of mild base can prevent it.

43. Use of pH in everyday life
➔ Self defence of animals and plants: Nettle plant have fine stinging hair which
inject methanoic acid.
➔ Tooth decay: tooth enamel is made of calcium phosphate which hardest
substance in our body. If we didn’t wash our mouth properly after every meal,
the food particles and sugar remaining in mouth produces acids with the help
of bacterias in our mouth. If its pH goes below 5.5 it cause to corrode the
tooth enamel and tooth decay.

46. Formation of salts
1) By neutralization of acids and bases
NaOH + HCl → NaCl + H2O
1) By action of acid on metals
Zn + H2SO4 → ZnSO4 + H2
1) By action of acid on metal carbonates and hydrogen carbonates
CaCO3 + 2HCl → CaCl2 + H2O +
CO2
NaHCO3 + HCl → NaCl + H2O
+ CO2

47. Types of salts
Acid Base Nature of Solution pH (at 25oC)
Strong Strong Neutral pH=7
Weak Strong basic pH>7
Strong Weak acidic pH<7
Weak Weak More information
required
_

48. Some commonly used salts
1. Baking soda
➔ Sodium hydrogen carbonate (NaHCO3)
➔ Manufacturing is through Solvay's process
➔ Raw Materials required: Limestone (CaCO3), Sodium Chloride (NaCl) in the
form of brine, Ammonia (NH3).
➔ Process: A. CaCO3 →(Heating) CaO + CO2
B. NaCl + CO2 + NH3+ H2O → NaHCO3 + NH4Cl
C. 2NaHCO3 →(Heating) Na2CO3+ H2O+ CO2
➔ Uses: Cooking of certain foods, baking powder, medicine,
soda acid fire extinguisher.

49. Some commonly used salts
2. Washing soda
➔ Sodium carbonate decahydrate (Na2CO3 10H2O)
➔ Raw Materials required: Limestone (CaCO3), Sodium Chloride (NaCl)
in the form of brine, Ammonia (NH3).
➔ Manufacture:
2NaHCO3 →(Heating) Na2CO3+ H2O+ CO2
Na2CO3+10H2O → Na2CO3 10H2O
Uses: Caustic soda, glass, soap powder, paper industry, to remove
permanent hardness of water, cleaning agent.

50. Some commonly used salts
3. Plaster of paris
➔ POP- Calcium sulphate hemihydrate (2 CaSO4. ½ H2O)
➔ Raw Materials required: Gypsum(2 CaSO4.2 H2O).
➔ Manufacture:
2 CaSO4.2 H2O →(Heating 100oC) 2 CaSO4. ½ H2O + 3/2 H2O
Uses: making toys, chalk, fire proof materials, ceilings, wall, pillars.

51. Some commonly used salts
4. Bleaching powder
➔ Calcium oxychloride (CaOCl2)
➔ Raw Materials required: Slaked lime (Ca(OH)2), Chlorine gas (Cl2).
➔ Manufacture: Hasenclever process.
(Ca(OH)2 + Cl2 → CaOCl2 + H2O
Uses: textile industry, bleaching of wood pulp, to make wool
unshrinkable.

52. Thanks…