NCERT CBSE Board Solution for Class 10 Science Chapter 1 Chemical Reactions and Equations notes video and question-answer and chapter related all best resource.
NCERT Solutions for Class 10 Science Chapter 1 chemical reactions and equations Video Notes
Class 10th Science Other Chapter Solutions
A chemical reaction is a process in which the initial substances change to form a new substance. Chemical reactions involve chemical changes.
The reaction through which the chemical properties of a substance are changed is called a chemical reaction.
Chemical Equation are representation of chemical reaction by means of symbols of substances in the form of formula is called chemical equation.
Magnesium gets covered with a layer of magnesium oxide when kept in air for a long time. This layer hinders the burning of magnesium. Hence, it is to be cleaned before burning.
Magnesium rubber should be cleaned before burning in air because Magnesium metal reacts with the atmospheric oxygen and forms Magnesium Oxide (MgO) layer which is a very stable compound. In order to prevent further reactions with Oxygen, it is therefore necessary to clean the ribbon by to remove the layer of MgO.
(i) Physical Change
(ii) Chemical Change
A balanced equation is the one in which number of different atoms on both the reactant and product sides are equal. Balancing chemical equation is necessary for the reaction should obey The Law of Conservation of energy. Balancing the chemical equation has no defined method and is purely a trial and error attempt.
A balanced chemical equation has an equal number of atoms of different elements in the reactants and products.
The chemical equations should be balanced to satisfy the law of conservation of mass.
these are basically five types:
i. Combination Reaction
ii. Decomposition Reaction
iii. Displacement Reaction
iv. Double Displacement Reaction
v. Redox Reaction
An endothermic reaction occurs when energy is absorbed from the surroundings in the form of heat.(Example: Photosynthesis, melting of ice, evaporation). Conversely, an exothermic reaction is one in which energy is released from the system into the surroundings. (Example: Explosions, concrete setting, nuclear fission and fusion).
For the survival of life, we require energy. We obtain this energy from the food we eat. The food molecules, through the process of digestion, is broken down into a simpler molecule like glucose. These substances come in contact with the Oxygen present in our body cells to form Carbon dioxide and water along with a certain amount of energy (Respiration process). Since the energy is in the form of heat (that maintains our body temperature) the respiration is considered to be an exothermic reaction.
The reaction taking place is:
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Combination reaction is said to be the reaction between two or more molecules to form a larger molecule; whereas the decomposition reaction is defined as the splitting of larger molecules into two or more smaller molecules. This essentially explains that the decomposition reaction is the opposite of the combination reaction.
In most of the cases the decomposition reaction is endothermic since heat from the surrounding or induced heat is used to break the bonds of the larger molecule. Few examples of decomposition reactions are:
ZnCO3 → ZnO + CO2
CaCO3 + Energy → CaO + CO2
2HgO → 2Hg + O2
NCERT Solution for class 10 Science Chapter 1 Chemical reactions and equations
- Write one equation each for decomposition reactions in which energy is supplied in the form of heat, light or electricity.
(a) Thermal decomposition reaction (Thermolysis)
Decomposition of potassium chlorate (KClO3) : When heated strongly, potassium chlorate decomposes into potassium chloride and oxygen. This reaction is used for the preparation of oxygen.
2KClO3 + Heat → 2KCl + 3O2
(b) Electrolytic decomposition reaction (Electrolysis)
Decomposition of sodium chloride (NaCl) : On passing electricity through molten sodium chloride, it decomposes into sodium and chlorine.
NaCl → Na + Cl2
(c) Photo decomposition reaction (Photolysis)
Decomposition of hydrogen peroxide (H2O2): In the presence of light, hydrogen peroxide decomposes into water and oxygen.
2H2O2 (Light)→ 2H2O + O2
- What is the difference between displacement and double displacement reactions? Write relevant equations for the above.
A displacement reaction is the one when a more reactive substance displaces a less reactive one from its salt solution whereas a double displacement reaction is the one where a mutual exchange of ions happens between two compounds.
In a displacement reaction, only a single displacement takes place whereas in the double displacement reaction, as the name suggests two displacement takes place between the molecules.
Mg + 2HCl → MgCl2 + H2
Double displacement reaction
2KBr + BaI2 → 2KI + BaBr2
- What is Corrosion?
It is an undesirable change that occurs in metals when they are attacked by moisture, air, acids, and bases.
Example: Corrosion (rusting) of Iron: Fe2O3.nH2O (Hydrated iron oxide)
- What is Rancidity?
The taste and odor of food materials containing fat and oil change when they are left exposed to air for a long time. This is called Rancidity. It is caused due to the oxidation of fat and oil present in food materials.
- Methods to prevent rancidity?
By adding anti-oxidant.
Replacing air by nitrogen.
Refrigeration of foodstuff.
- Why should a magnesium ribbon be cleaned before burning in air?
Magnesium rubber should be cleaned before burning in air because Magnesium metal reacts with the atmospheric oxygen and forms Magnesium Oxide (MgO) layer which is a very stable compound. In order to prevent further reactions with Oxygen, it is therefore necessary to clean the ribbon by to remove
the layer of MgO.
- Write a balanced equations for the following chemical reactions.
i) Hydrogen + Chloride —-> Hydrogen chloride
ii) Barium chloride + Aluminium sulphate —-> Barium sulphate + Aluminium chloride
iii) Sodium + Water —-> Sodium hydroxide + Hydrogen
i) H2 + Cl2→ 2HCl
ii) 3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4
iii) 2Na + 2H2O → 2NaOH + H2
- Write a balanced chemical equation with state symbols for the following reactions
i) Solutions of Barium chloride and Sodium sulphate in water react to give insoluble Barium sulphate and solution of Sodium chloride.
ii) Sodium hydroxide solution in water reacts with hydrochloric acid solution to produce Sodium chloride solution and water.
i) BaCl2 + Na2SO4 → BaSO4 + 2NaCl
ii) NaOH + HCl → NaCl + H2O
- Chapter 1: Chemical Reactions and Equations
- Chapter 2: Acids, Bases, and Salts
- Chapter 3: Metals and Non-Metals
- Chapter 4: Carbon and its Compounds
- Chapter 5: Periodic Classification of Elements
- Chapter 6: Life Processes
- Chapter 7: Control and Coordination
- Chapter 8: How do Organisms Reproduce?
- Chapter 9: Heredity and Evolution
- Chapter 10: Light – Reflection and Refraction
- Chapter 11: Human Eye and Colourful World
- Chapter 12: Electricity
- Chapter 13: Magnetic Effects of Electric Current
- Chapter 14: Sources of Energy
- Chapter 15: Our Environment
- Chapter 16: Management of Natural Resources
- A solution of a substance ‘X’ is used for whitewashing.
(i) Name the substance ‘X’ and write its formula.
(ii) Write the reaction of the substance ‘X’ named in (i) above with water.
i)The substance ‘X’ which is used in whitewashing is quick lime or Calcium Oxide and its formula is CaO.
CaO + H2O → Ca(OH)2
- Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount
collected in the other? Name this gas
In activity 1.7, gas collected in one of the test tubes is double of the amount collected in the other because water gets hydrolysed to release H2 and O2 gas. Here, after electrolysis two molecules of Hydrogen and one molecule of oxygen gas is released, hence the amount of Hydrogen collected would be double than that of oxygen.