CBSE Class 10 Science Chapter 2 Revision Notes
Chapter 2: Acids, Bases and Salts Revision Notes
Classification of Matter
on the basis of
a) Composition– elements, compounds, and mixes
b) State of matter- Solids, liquids and gases
c) soluble matter – suspensions, colloids, and solutions
- Homogeneous and heterogeneous mixes are two types of mixtures.
- Covalent and ionic compounds are two different types of chemicals.
What Is the Difference Between an Acid and a Base?
Physical examination
There are two physical tests that may be used to determine if an acid or a base is present.
a. Taste
- An acid has a sour flavour, whereas a base has a bitter flavour.
- Because an acid or a base might be polluted or caustic, this way of tasting is not recommended.
b. Effect on Indicators by acids and bases
- When a chemical substance comes into touch with an acid or a base, it changes its physical qualities, most commonly colour or scent.
The following are some regularly used indicators and the many colours they display:
a) Litmus paper
- Purple in a neutral solution
- In an acidic solution, the colour is red.
- Blue is the most basic answer.
- Litmus is also available as paper strips in two colours: red and blue litmus.
- A damp blue litmus paper turns red when exposed to an acid.
- A base changes the colour of wet red litmus paper to blue.
b) Methyl orange
- Orange in a neutral solution
- In an acidic solution, the colour is red.
- Yellow in basic solution
d) Phenolphthalein
- In a colourless neutral solution
- In an acidic solution, the substance stays colourless.
- Pink is the most basic answer.
WATER
- Water contains acids and bases.
- Acids and bases breakdown into their respective ions when introduced to water and aid in the conductivity of electricity.
What is the distinction between a base and an alkali?
- Acids react with bases to neutralise them.
- Metal oxides, metal hydroxides, metal carbonates, and metal bicarbonates make up these compounds.
- The majority of them are water insoluble.
- An alkali is a base in aqueous solution (mainly metallic hydroxides).
- It dissolves in water and then dissociates to produce the OH ion.
- All bases are alkalis, but not all alkalis are bases.
Hydronium ion
- A coordinate covalent bond is created when a hydrogen ion receives a lone pair of electrons from the oxygen atom of a water molecule.
Dilution
- Dilution is the process of decreasing a solution’s concentration by adding more solvent (typically water).
- It’s a really exothermic reaction.
- Acid must be put to water, not the other way around, to dilute it.
STRENGTH OF ACID AND WATER
- When all molecules of an acid or a base disintegrate entirely in water to produce their corresponding ions, H+(aq) for acid and OH(aq) for base).
Weak acid or base: When just a few molecules of an acid or base dissociate in water to produce their corresponding ions, H+(aq) for acid and OH(aq) for base.
Universal Indicator
- The pH range of a universal indicator is 0 to 14, and it represents the acidity or alkalinity of a solution.
- The pH of a neutral solution is 7.
pH
- The pH scale spans from 0 to 14, with 0 being the most acidic and 14 being the most alkaline.
- If the acidic solution has a pH of 7, it is said to be acidic.
- If the pH is more than 7, use a basic solution.
Importance of pH in everyday life
1. Plant and animal pH sensitivity
- pH affects both plants and animals. At a given pH value, vital life activities such as food digestion, enzyme functioning, and hormone production take place.
2. A soil’s pH
- The pH of a soil that is ideal for plant or agricultural growth is 6.5 to 7.0.
3. The digestive system’s pH
- In human stomach, digestion takes place at a precise pH range of 1.5 to 4.
- HCl in our stomach influences the pH of enzyme interactions as food is being digested.
4. The role of pH in tooth decay
- When the teeth are exposed to an acidic environment with a pH of 5.5 or lower, tooth decay occurs.
5. The pH of animal and plant self-defense
- Animals and plants employ acidic compounds as a self-defense strategy.
- For self-defense, bees and plants like nettle emit a very acidic chemical. These acidic chemicals released have a specified pH.
SALTS
- A salt is a compound made up of an acid’s anion and a base’s cation.
- KCl, NaNO3, CaSO4, and other salts are examples.
- The neutralisation reaction of an acid and a base is commonly used to make salts.
Common salt
- Because it is used in cooking all around the world, sodium chloride (NaCl) is known as common salt.
Family of Salt
- Salts with the same cation or anion are classified as belonging to the same family. NaCl, KCl, and LiCl, for example.
The salts’ pH
- In nature, a salt comprising a strong acid and a strong base will be neutral. pH 7.0 (approx.).
- In nature, a salt of a weak acid and a strong base will be basic. pH greater than 7.
- Acidic in nature is a salt comprising a strong acid and a weak base. pH is less than 7.
- A pH test is used to detect the pH of a salt of a weak acid and a weak base.
Bleaching powder
- Bleaching powder produces chlorine when it comes into contact with water, which is responsible for the bleaching effect.
Baking soda
- Sodium hydrogen carbonate is the chemical name for this substance.
- NaHCO3 is the chemical formula.
Uses:
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Textile manufacturing
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Paper manufacturing
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Antiseptic
Washing soda
- Sodium hydrogen carbonate is the chemical name for this substance.
- NaHCO3 is the chemical formula.
Preparation (the Solvay method) –
a. Limestone is heated in the following way: CaCO3 + CaO + CO2
b. CO2 is passed through a concentrated sodium chloride/ammonia solution:
NaHCO3(aq) + NH4Cl = NaCl(aq) + NH3(g) + CO2(g) + H2O(l) (aq)
Uses
In the glass, soap, and paper industries, for example.
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Water softening
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A housecleaner
Plaster of paris
- Heating gypsum, CaSO4.2H2O (s) to 100°C (373K) yields CaSO4. 12 H2O and 3/2 H2O.
- Plaster of Paris is made up of CaSO4 and 12 H2O.
- CaSO4. 12 H2O denotes that two CaSO4 formula units share one water molecule.
- Casts are used to help mend fractures.