Last updated on February 6th, 2024 at 12:50 am
CG Board Class 8 Chemical Reactions When and What Type
Chhattisgarh Board Class 8 Science Chapter 4 Solution Textbook question and answers as well as extra question and answers from the chapter
What do you understand by chemical reaction?
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. It involves the breaking and forming of chemical bonds, resulting in the creation of new substances with different properties.
Burning of candle is a chemical reaction. Give the properties connected with this.
Burning of Candle Properties:
- Heat Production: The burning candle releases heat.
- Light Emission: The flame produces light.
- Formation of Gases: Combustion produces carbon dioxide and water vapor.
- Change in State: The wax melts and then vaporizes.
What are reactants and products? Explain with examples.
Reactants: These are the substances present at the beginning of a chemical reaction. In the reaction CaCO3 → CaO + CO2, CaCO3 is the reactant.
Products: These are the substances formed as a result of the chemical reaction. In the same reaction, CaO and CO2 are the products.
Explain the following reactions with two examples each.
Combination
Example 1: 2Mg + O2 → 2MgO (Magnesium + Oxygen → Magnesium Oxide)
Example 2: N2 + 3H2 → 2NH3 (Nitrogen + Hydrogen → Ammonia)
Decomposition
Example 1: 2H2O → 2H2 + O2 (Water → Hydrogen + Oxygen)
Example 2: 2KClO3 → 2KCl + 3O2 (Potassium Chlorate → Potassium Chloride + Oxygen)
Displacement
Example 1: Zn + 2HCl → ZnCl2 + H2 (Zinc + Hydrochloric Acid → Zinc Chloride + Hydrogen)
Example 2: CuSO4 + Zn → ZnSO4 + Cu (Copper Sulfate + Zinc → Zinc Sulfate + Copper)
Precipitation
Example 1: AgNO3 + NaCl → AgCl + NaNO3 (Silver Nitrate + Sodium Chloride → Silver Chloride + Sodium Nitrate)
Example 2: Ca(OH)2 + CO2 → CaCO3 + H2O (Calcium Hydroxide + Carbon Dioxide → Calcium Carbonate + Water)
If you prepare lime water and leave it open. What changes will taken place in this solution next day and why?
If lime water is left open, it absorbs carbon dioxide from the air, forming calcium carbonate, causing the solution to turn milky due to the insoluble precipitate.
What is neutralization reaction? Give one example.
A neutralization reaction is a chemical reaction between an acid and a base, producing a salt and water. Example: HCl + NaOH → NaCl + H2O (Hydrochloric Acid + Sodium Hydroxide → Sodium Chloride + Water)
What is precipitate? Write a reaction in which a precipitate is formed.
A precipitate is an insoluble solid formed during a chemical reaction in a solution. Example: AgNO3 + NaCl → AgCl (precipitate) + NaNO3
Choose the correct answer
- NaOH + HCl NaCl + H2O this is a:-
(a) Decomposition reaction (b) Combination reaction
(c) Neutralization reaction (d) Precipitation reaction
(c) Neutralization reaction
- On ignition when a substance combines with oxygen, the process is called :-
(a) reduction (b) oxidation (c) decomposition (d) displacement
(b) Oxidation
