Chemical Reactions and Equations class 10 Chemistry complete and short notes fully explained. Guarantee 95%+ marks.

Chemical Reactions and Equations class 10 Chemistry complete and short notes fully explained:

Chemical Reactions and Equations class 10 Chemistry- Introduction to change:

• A process in which the final state of the substance is different
  from its initial or original state is known as Change.

Chemical Reactions and Equations class 10 Chemistry- Classification of changes:

• On the basis of Change of Composition : 

1. physical change. ex- melting of ice, meting of candle wax etc.
2. chemical change. ex- rusting of iron, ripening of fruit, burning of wood etc.

Chemical Reactions and Equations class 10 Chemistry- Physical Change:

• Shape/Size/Physical state change
• example- melting of Ice, crumpling of paper.

Chemical Reactions and Equations class 10 Chemistry- Chemical Change:

• Chemical composition changes along with a change in
  shape/size/state changes.
• example- Rusting of Iron or burning of wood etc.

Note- When Candle burns both Physical and Chemical Changes takes place. Burning of a candle is both a chemical and a physical reaction. The physical change occurs when the wax of candle melts and it loses its shape. The chemical change is combustion of fuel in presence of oxygen to produce carbon dioxide.

Chemical Reactions and Equations class 10 Chemistry- Chemical equation:

• A chemical equation shows a chemical reaction using symbols and formulas to represent the reactants and products involved.
• For eg: Hydrogen (H2) + Oxygen (O2) → Water (H2O)

Chemical Reactions and Equations class 10 Chemistry- Chemical reaction:

• A chemical reaction is a process in which substances transform, resulting in the formation of new substances with different chemical properties.

Chemical Reactions and Equations class 10 Chemistry- Characteristics of a Chemical reaction:

I. Change in Colour:
Fe + CuSO4 (Blue) → FeSO4 (Blue-green) + Cu

II. Change in Temperature:
CaO + H2O → Ca(OH)2 + Heat

III. Change in State:
H2 (g) + O2 (g)→ H2O (i.e. from gas to liquid)

IV. Evolution of gas:
Zn(s) + H2SO4 (aq) →ZnSO4(aq)+H2(g)

V. Formation of precipitate:
Pb(NO3 )2 (aq) + Kl (aq) → Pbl2 (s) + KNO3 (aq)

VI. Endothermic reaction (energy is absorbed):
CaCO3 + Heat → CaO + CO2 (photosynthesis is an endothermic
reaction)

VII. Exothermic reaction (energy is released):
CaO + H2O → Ca(OH)2 + Heat (Digestion and respiration are
exothermic reactions)

Chemical Reactions and Equations class 10 Chemistry- Representing Chemical Reaction:

• When magnesium ribbon is strongly heated in the
  presence of oxygen it burns with a dazzling white flame
  and forms white magnesium oxide powder.
• Reactants(s) -> Substances that undergo a chemical
  change/chemical reaction.
• Products(s) -> Substances formed as a result of
  chemical change.

Chemical Reactions and Equations class 10 Chemistry- Balancing Chemical Equation:

• Follows the law of conservation of mass wherever written or
  represented.
• In simpler chemical reactions, mass is neither created nor destroyed,
  i.e., mass of reactants is equal to mass of products.
• No of atoms (Reactants) No of atoms (Products)

ex- ⇒Fe + H2O = Fe3O4+ H2

Step 1. Writing the chemical reaction in word form.
Iron + Steam → Magnetite + hydrogen gas

Step 2. Writing the chemical symbols in the form of a skeletal chemical
equation.

Step 3. Enclose the chemical symbol(s) and formulae in boxes, this
ensures the subscript of the symbol or formula is not changed in order
to make the number of atoms the same on both sides of the chemical
equation.

Step 4. List the number of atoms of different elements.

Step 5. Start balancing the compound (reactant of product) that
contains the maximum number of atoms. In that compound, balance
the element with the maximum number of atoms.

⇒3Fe + 4H2O = 4Fe3O4+ 4H2 (balanced equation)

What is Catalyst??

• A substance that increases or decreases the reaction without itself being consumed in the reaction.
• example: 1)Formation of ammonia (Haber’s Process) – Fe (+ve catalyst)
  2)Decomposition of Hydrogen peroxide – Phosphoric acid (-ve catalyst)

Chemical Reactions and Equations class 10 Chemistry- Types of Chemical Reaction:

1. Combination reaction.
2. Decomposition reaction.
3. Displacement reaction.
4. Double Displacement Reaction.

Combination reaction:

• A chemical reaction in which two or more  elements or compounds (reactants) react to form a single compound (product).
• Types of combination reactions possible:
  i. Combination of two elements to form a compound. Example: Burning of Magnesium ribbon
  ii. Combination of two compounds to form a compound. Example: Quicklime (CaO) with water
  iii. Combination of an element and a compound to form a compound. Example: Oxidation of sulphur dioxide ⇒ S(s) + O2(g) SO2(g) 2SO2(g) + O2(g) 2SO3(g)

 

Decomposition Reaction:

• Chemical decomposition, or chemical breakdown, is the process or effect of simplifying a single chemical entity into two or more fragments.
• example:

1. 2HgO(s)→2Hg(l)+O2(g)
2. CaCO3(s)→CaO(s)+CO2(g)
3. 2NaOH(s)→Na2O(s)+H2O(g)
4. H2CO3(aq)→CO2(g)+H2O(l)

Displacement Reaction:

• A displacement reaction is the one wherein the atom or a set of atoms is displaced by another atom in a molecule.
• For example, when iron is added to a copper sulphate solution, it displaces the copper metal.
• more example:

1. Fe(s) + CuSO4(aq) ⇒ FeSO4(aq) + Cu(s)
2. Zn(s) + CuSO4(aq) ⇒ ZnSO4(aq) + Cu(s)
3. Pb(s) + CuCl2(aq) ⇒PbCl2(aq) + Cu(s)
4. Cu(s) + 2AgNO3(aq)⇒ Cu(NO3)2(aq) + 2Ag(s)
5. Cl2(g) + 2KBr(aq)⇒ 2KCl (aq) + Br2 (l)

• All displacement reactions are exothermic, i.e. heat is evolved.

Double Displacement Reaction:

• A chemical reaction in which there is an exchange of ions, i.e., cations and anions between reactants.
• example-

1. AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)
2. 2AgNO₃(aq) + CaCl₂(aq) → 2AgCl(s) + Ca(NO₃)₂(aq)

• Double displacement reaction- 1) Precipitation Reactions

2) Neutralisation Reactions

3) Gas forming reactions

Precipitation reaction:

• The reaction in which aqueous solutions of two ionic compounds or a gas and an aqueous solution of ionic compound react to form an insoluble solid, i.e., precipitate.
• Example:

1. Pb(NO3)2 (aq) + 2KI (aq)⇒ PbI2(yellow precipitate) + 2KNO3 (aq)
2. BaCl2 (aq) + Na2SO4 (aq) ⇒ BaSO4(White ppt) + 2NaCl (aq)
3. Ba(OH)2 (aq) + CO2(g) ⇒ CaCO3(s) + H2O (l)

Neutralization Reaction:

• The reaction in which an acid reacts with a base to form salt and water.
• Example: HCl (aq) + NaOH (aq)⇒ NaCl (aq) + H2O (l)

Gas Forming Reaction:

• The reaction in which a a gas is produced as a product from the reactants
  not in the gaseous state.
• Example: CH3OOH(aq) + NaHCO3(s)⇒ NaCH3COO (aq) + H2CO3

Chemical Reactions and Equations class 10 Chemistry- Oxidation Reaction:

• Addition of oxygen
• Removal of hydrogen

Chemical Reactions and Equations class 10 Chemistry- Reduction Reaction:

• Addition of a hydrogen
• Removal of oxygen

Chemical Reactions and Equations class 10 Chemistry- Redox Reaction:

• A chemical reaction in which reduction and oxidation takes place
  simultaneously.
• Example: PbO ( s ) (Lead oxide) + H 2 ( g ) (Hydrogen) → Pb ( s ) (Lead) + H 2 O ( l ) (Water)

Chemical Reactions and Equations class 10 Chemistry- Effects of oxidation in daily life:

1) Corrosion:

• When metal surfaces are attacked by substance around it such as oxygen, moisture, acids, etc., it is said to corrode and this process is called corrosion.
• It is undesirable since it reduces strength & fades its appearence.
• Example:

1. Fe + O2 + H2O ⇒ Hydrated iron oxide – Reddish
2. Cu + CO2 + H2O ⇒ Copper Carbonate – Bluish – green
3. Ag + S ⇒ Silver Sulphide – Black

• Prevention: 

1. Painting
2. Oiling and Greasing
3. Alloying
4. Galvanisation
5. Chrome plating

2) Rancidity:

• It is the oxidation of oil or fat-containing food items when they are kept in the open for a long time, resulting in an unpleasant odour and taste.
• examples:

1. Oxidative rancidity ( of oxygen)
2. Microbes (e.g., bread mold, etc.)
3. Hydrolytic ( of water)

• Prevention:

1. Addition of antioxidants: Some chemical substances are added to the fat and oil-containing substances that inhibit their oxidation. Such substances are called antioxidants.
2. Filling nitrogen gas: In chip packets, the oxygen gas is replaced with nitrogen to prevent the oxidation of chips. Moreover, nitrogen does not react with the chips to change their odour and taste. Hence, the chips retain their original taste and odour
3. Refrigeration of food items: It lowers down the oxidation of food items and prevents a change in their odour and taste.

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