This quick revision notes on Acids, Bases and Salts Class 10 Science includes indicators, properties of acids and bases, pH scale, salts, baking soda, washing soda,
bleaching powder, POP and daily life applications of pH.
Acids, Bases and Salts is chapter 2 of class 10 Science of RBSE and one of the most important chapters for board exams. After reading these notes, you can solve questions of the chapter and practice with MCQs for better understanding.
Here you will find quick revision notes in easy language for fast learning and last-minute revision.
What are acids?
The substances that produce H+ ions in aqueous solution. Examples: HCl, H2SO4,
HNO3 , CH3COOH
What are Bases?
The substances that produce OH– in aqueous solution. Examples – NaOH,
KOH , Ca(OH)2
What are alkalis?
The bases that are soluble in water are known as alkalis. Examples- – NaOH,
KOH, NH4OH
What are salts?
The compounds formed by the neutralization reaction between an acid and a base.Examples- NaCl, KCl, NH4Cl
What are indicators?
An indicator is a substance what show the nature of a solution (acid or base) by changing its colour or smell.
Types of indicators
(i) Natural indicators
(ii) Synthetic indicators
(iii) Olfactory indicators
(i) Natural indicators– These are obtained from natural sources. Examples – litmus, turmeric, red cabbage, china rose etc
(ii) Synthetic indicators – These are chemical compounds. Examples – Methyl orange, phenolphthalein.
(iii) Olfactory indicators– Substances whose smell changes in acidic or basic medium. Examples – onion, vanilla essence, clove oil.
Chemical Properties of Acids
(i) Reaction with metals – Acid reacts with metal to produce salt and hydrogen gas.
Acid + Metal →Slat + Hydrogen
HCl + Zn → ZnSO4 + H2↑
(ii) Reaction with metal carbonates – Salt, carbon dioxide and water are produced.
Metal carbonates + Acids → salts + CO2 + Water
Na2CO3 + 2HCl →2NaCl + CO2 + H2O
CO2 turns lime water milky due to formation of calcium carbonate.
(iii) Reaction with Metal hydrogen carbonates – Salt, carbon dioxide and water are produced.
NaHCO3 + HCl → NaCl + CO2 + H2O
(iv) Reaction with metallic oxide – Salt and water are formed. Metallic oxides are basic in nature.
Metal oxide + Acid→ Salt + water
CuO + HCl → CuCl2 + H2O
Chemical Properties of Bases
(i) Reaction with acids – Salt and water are formed. The reaction is called neutralization reaction.
Base + Acid → Salt + Water
NaOH + HCl → NaCl +H2O
(ii) Reaction with metals – Salt and hydrogen gas are formed.
Zn + NaOH →Na2ZnO2 + H2
Solution of Acids and Bases conduct Electricity
Acids and bases conduct electricity only in aqueous solution because they produce ions when dissolved in water.
When acids are dissolved in water, they produce hydrogen ions.
HCl + H2O →H3O+ + Cl–
(Hydrogen ions remain as hydronium ions in water)
When bases are dissolved in water, they produce hydroxyl ions.
NaOH + H2O → Na+(aq) +OH–(aq)
These free ions conduct electricity.
Strength of Acids and Bases
Strength of acids and bases depends on the concentration of H+ and OH– ions
which is measured using the pH scale.
What is pH?
pH is the measure of the concentration of hydrogen ions in a solution.
pH scale range is from 0 to 14.
|
pH |
Nature |
|
0- 6 |
Acidic |
|
7 |
Neutral |
|
8-14 |
Basic |
Lower pH show the more concentration of hydrogen ions.
Higher pH shows the more concentration of hydroxyl ions.
Importance of pH in Everyday Life
i. Human body – Human body pH range is 7.0- 7.8
ii. Acid rain – When pH of rain water becomes lower then 5.6, it is called acid rain. It damages plants, soil and pollute water bodies.
iii. Digestive system– Stomach produces hydrochloric acid which helps in digestion. Excess acid is produced during indigestion. Milk of magnesia (Mg(OH)2) is a mild base which is used as antacid.
iv.Tooth decay – pH of mouth becomes lower than 5.5 causes tooth decay. Toothpaste neutralize acid in the mouth.
v. Bee sting – Bee sting release acid that causes irritation. Baking soda gives relief.
Salts and their Nature
Salts are formed by the reaction of acid and base. Their nature depends on the strength of acids and bases.
|
Acid and base |
Nature of salt |
|
Strong acid + strong base |
Neutral |
|
Strong acid + weak base |
Acidic |
|
Weak acid + strong base |
Basic |
Chemical formula – NaOH
Preparation – Chlor alkali process
Reaction – 2NaCl + 2H2O →2NaOH + H2
(ii) Bleaching powder
Chemical formula – Ca(OCl)2
Preparation – Chlorine is passed on dry calcium hydroxide.
Reaction – 2Ca(OH)2 + 2Cl2 →Ca(OCl)2 +CaCl2 + 2H2O
Uses – In water purification, bleaching clothes, disinfectant, oxidizing agent
(iii) Baking soda
Formula – NaHCO3
Preparation Method
NaCl + H2O +CO2 + NH3 →NH4Cl + NaHCO3
Heating of baking soda
2NaHCO3→ Na2CO3 + H2O + CO2
Uses – It is used in baking, as antacid, fire extinguisher
(iv) Washing Soda
Formula – Na2CO3.10H2O
Preparation method – Sodium carbonate is obtained by heating of baking soda. Washing soda is obtained by crystallization of sodium carbonate.
Na2CO3.10H2O → Na2CO3 + 10H2O
Uses – In glass industry, soap industry, cleaning agent, softening of hard water,
(v) Plaster of Paris (POP)
Formula – CaSO4.1/2H2O
Preparation method
By heating gypsum (CaSO4.2H2O)
Uses – Plaster on fractured bone, making toys and idols, moulds and casting.
Water of Crystallization
The fixed number of water molecules present in one formula unit of a salt is called water of crystallization.
Examples
CuSO4.5H2O
Na2CO3.10H2O
CaSO4.2H2O
Key Revision Points
i. Acids produce H+ ions.
ii. Bases produce OH– ions.
iii. pH is the measure of strength of acids and bases.
iv. pH affects life, health, soil and environment
v. NaCl is the raw material in making baking soda, washing soda, sodium hydroxide.
Acids, Bases ands Salts Short Questions with Answers
Q1. What is an acid?
Answer – An acid is a substance that produces H+ ions in aqueous solution.
Q2. What is a base?
Answer – A base is a substance that produces OH– in aqueous solution.
Q3. What is an alkali?
Answer – A base that is soluble in water is called an alkali.
Q4. What is a slat?
Answer – A salt is
formed by the neutralization reaction between an acid and a base.
Q5. Name two natural indicators.
Answer – Litmus and turmeric
Q6. Name two synthetic indicators.
Answer – Methyl oranges and phenolphthalein
Q7. What is an olfactory indicator?
Answer – An indicator that shows change by smell with an acid or base.
Q8. Which gas is evolved when an acid reacts with a metal?
Answer – Hydrogen gas
Q9. Which gas is evolved when an acid reacts with metal
carbonate?
Answer – Carbon dioxide
Q10. What is a neutralization reaction?
Answer – When an acid and base reacts to form a salt and water and neutralize each other.
Q11.What is pH scale?
Answer – The scale used to measure acidity or basicity of a solution. Its range is from 0 to 14.
Q12. What is the pH of a neutral solution?
Answer – 7
Q13. What is an antacid?
Answer – A basic substance used to neutralize excess acid in the stomach.
Q14.What is water of crystallization?
Answer – The fixed number of water molecules present in a salt is called water of crystallization.
Q15. What is the full form POP?
Answer – Plaster of Paris
Related Topics
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