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प्रश्न
What do you understand by 'chemical reaction'?
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उत्तर
A chemical reaction is the process of breaking the chemical bonds of the reacting substances (reactants) and making new bonds to form new substances (products).
A chemical change or chemical reaction occurs when particles collide. Collisions occur when reactants are in close contact or by supply of energy.
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संबंधित प्रश्न
Classify the following reaction as combination, decomposition, displacement, precipitation and neutralization. Also balance the equation.
\[\ce{NH3_{(g)} + HCl_{(g)} -> NH4Cl_{(s)}}\]
Give an example of a photochemical reaction.
Explain the term ‘chemical reaction’ with special reference to – ‘reactants’ and ‘products’.
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Addition of dilute acid to an active metal.
Complete the table given below.
| Heat on sodium chloride | Colour imparted to flame during flame test |
What kind of a change is associated with decaying of a plants?
Arrange the following statements in correct sequence:
- One side is water-loving and other water-hating molecules.
- When you agitate the cloth, the dirt is surrounded by many molecules and taken away from the cloth.
- The dirt surrounded by the detergent molecules floats in the water making it dirty.
- Finally, the cloth is clean.
- The detergent molecules have two sides.
- Water hating goes and joins with dirt and oil in the cloth while the water-loving joins with the water molecules.
Classify the following as physical or chemical properties
Most metal oxides form alkalis on interacting with water.
A chemical change may involve –
Give two examples for the following case:
Chemical changes
