Acids, Bases And Salts- Science Notes for CTET 2020: FREE PDF

EVS/ Science Study Notes Free PDF

In many teaching exams including CTET 2020, UPTET 2020 STET 2020 etc. Science may be an interesting subject having and 30 questions of Science content and 30 questions of Science Pedagogy in CTETand other State TET Exams. Science comprising of various branches of studies like chemistry, physical science, and life science.

ACIDS, BASES AND SALTS

What is an acid and a base?
Acid: Acids are substances that taste sour and are corrosive in nature.
Base: Bases are substances that, in aqueous solution, are slippery to the touch and bitter in taste.

Bronsted Lowry theory:
• A Bronsted acid is an H+ (aq) ion donor.
• A Bronsted base is an H+ (aq) ion acceptor.

Example:
In the reaction: HCl (aq) +NH3 (aq) →NH+4(aq) +Cl− (aq)
HCl – Bronsted acid and Cl− : its conjugate acid
NH3 – Bronsted base and NH+4 : its conjugate acid

I. Acids:
Difference between Weak Acid and Strong Acid:
Strong Acid: All mineral acids are strong acids except carbonic acid. For example: sulphuric acid, hydrochloric acid, nitric acid, phosphoric acid.
Weak Acid: All organic acids i.e. naturally occurring acids are weak acids. For example: tartaric acid, oxalic acid, formic acid, acetic acid, etc.

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Properties of Acids:
• Acids are sour in taste.
• Acids turn blue litmus to red.
• Acids release H+ ions.
• Arrhenius concept: contribute hydrogen ion to a solution.
• For example: Sulphuric Acid, Hydrochloric Acid etc.

A. Chemical properties of Acids:

1. Reaction of Acid with metals:
Acid + Metal → Salt + Hydrogen gas
(Mg  +  HSO4    →  H2    +  Mg SO4)

2. Reaction of Acid with Carbonate:
Acid + Carbonate → Salt + Water + Carbon Dioxide
(Na2CO3 + 2 HCl → 2NaCl + H2O + CO2)

3. Reaction of Acid with Base:
Acid + Base → Salt + Water
(HCl + NaOH → NaCl + H2O)

Uses of Acids in daily life:
1. Hydrochloric Acid: Used in the production of glucose from corn starch.
2. Carbonic Acid: Used in aerated drinks.
3. Sulphuric Acid: Used in car batteries.
4. Nitric Acid: Used in the manufacture of fertilizers, explosives

B. Bases:
• Bases are bitter in taste.
• Bases turn red litmus to blue
• Bases release OH- ions.
• Arrhenius concept: donate a hydrogen ion to aqueous solution.
• Bronsted-Lowery concept: Accept a proton in a chemical reaction.
For example: Sodium Hydroxide, Calcium Carbonate, Potassium Oxide Etc.

Chemical properties of bases:

1. Reaction of Base with salt:
FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl

2. Reaction of Base with Metals
2Al + 2NaOH + 2H2O → 2NaAlO2 + 3H2

3. Reaction of Acid with Base:
Acid + Base → Salt + Water
(HCl + NaOH → NaCl + H2O)

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Uses of Bases in Daily Life:
1. Sodium Hydroxide : Used in production of soaps, detergents, synthetic fibers.
2. Calcium Hydroxide: Used in the manufacture of bleaching powder, to make cement, lime water.
3. Magnesium Hydroxide: Used as an antacid (medicine that neutralizes acid in the stomach).
4. Ammonium Hydroxide: Used in the manufacture of fertilizers.
5. Aluminium Hydroxide: Used to make an antacid.

Physical properties of Acids and Bases:

S.No. Properties Acids Bases
1 Color Mineral acids are colorless. Some organic acids are white color solids Colorless except hydroxides of iron and copper
2 Taste Sour Bitter
3 Touch Slippery
4 Solubility Soluble in water Some bases are soluble in water
5 Confirmation test Turn blue litmus to red Turn red litmus to blue
6 PH value Lower than 7 Greater than 7
7 Example HCl NaOH

Similarity between Acids and Bases:
1. Both can react with water and produce ions in water.
2. Both of them changes color of litmus paper.
3. Both are good conductor of electricity.
4. Both form salt and water when react with each other

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Indicators:
Special types of substances are used to test whether the substance is acid or base. This is used as the confirmation test for the presence of acids.
These substances are called indicators. Some natural occurring indicators are
• Turmeric,
• Litmus (extracted from lichens),
• China rose petals.

Neutralization:
When an acidic solution is mixed with the basic solution, their acidity or basicity gets destroyed. Such reaction is called a Neutralization reaction. Salt is produced in the process with the evolution of heat.
Acid + Base → Salt + Water
(HCl + NaOH → NaCl + H2O)

Neutralization in Daily Life:
• During indigestion, taking milk of magnesia (magnesium hydroxide) gives us relief as it neutralizes the effect of excess acid produced inside the stomach.
• The effect of ant sting which is caused by formic acid can be neutralized by rubbing moist baking soda (basic in nature).
• To ensure that plants can grow well, the soil is treated with either acids or bases depending if it’s basic or acidic in nature.
• Factory wastes, generally being acidic in nature can cause environmental damage, are treated with basic substances before discharge.

pH Scale:
• To know how strong the acid or base is, pH scale had been developed by Soren Sorenson.
• ‘p’in the term pH stands for ‘potentz’.
• Numbers from 1 to 14 are marked on pH scale which indicates about acidity and basicity of the solution.
• pH of an acidic solution is ranging from 0 to 6
• pH of the basic solution is ranging from 8 to 14.
• pH of a neutral solution is 7, means the solution is neither acidic nor basic.

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Some important chemicals:

S.No. Chemical Name Chemical Formula Uses
1. Baking Soda NaHCO3 Used in deodorant, tooth whitening, prevent sunburns.
2. Washing Soda Na2CO3.10H2O Remove permanent hardness of water
3. Plaster of Paris CaSO4.1/2H2O Used for making toys, smooth the surfaces, decoration
4. Bleaching Powder  CaOCl2 Disinfect drinking water, oxidizing agent, helps in decolorizing.
5. Caustic Soda NaOH Manufacture of soaps, used in paper industry

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