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प्रश्न
State four conditions necessary for a chemical reaction to take place.
उत्तर
Ans: Close contact— For a chemical reaction to take place the reactants should be brought in close contact i.e., they should be mixed,
\[\ce{Sodium + Water -> Sodium hydroxide + Water}\]
Solution form— Some substances react with each other only when they are mixed in the solution form, e.g.,
\[\ce{\underset{\text{(aq.)}}{Silver nitrate} + \underset{\text{(aq.)}}{Sodium chloride} ->\underset{\text{(ppt.)}}{Silver nitrate}+\underset{\text{(aq.)}}{Sodium nitrate}}\]
Heat— Some reactants need to be heated to undergo a chemical change, e.g.,
\[\ce{Potassium chlorate->[heat] Potassium chloride + oxygen}\]
Light— Some reactions take place in the presence of light.
\[\ce{Carbon dioxide + Water ->[chlrophyll][sunlight] Glucose + Oxygen}\]
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संबंधित प्रश्न
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In a ............ change, new substances are formed.
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Write a short note on the information derived from a balanced chemical equation.
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A change in which the substance can be brought back to its original state is called a _______ change.
Match the pairs.
| a. | Photosynthesis | i. | Tendency to lose electrons |
| b. | Water | ii. | Reactant in combustion process |
| c. | Sodium chloride | iii. | Chemical change |
| d. | Dissolution of salt in water | iv. | Covalent bond |
| e. | Carbon | v. | Ionic bond |
| f. | Fluorine | vi. | Physical change |
| g. | Magnesium | vii. | Tendency to form anion |
Give an example of a reaction where the following are involved:
Solution
Give reason for the following:
Colourless concentrated sulphuric acid in a test tube changes to blue on adding a small piece of copper to it.
Complete and balance the following reaction:
Pb(NO3)2 + KI →
Complete and balance the following reaction:
\[\ce{Pb(NO3)2 ->[\Delta]}\]
State the original colour of the following substance and colour of residue obtained after heating.
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Give balanced equation for the following conversion affected by heat alone on the substance:
Copper nitrate to nitrogen dioxide
Give balanced equation for the following conversion affected by heat alone on the substance:
Ammonium dichromate to nitrogen
Complete the table given below.
| Heat on ammonium dichromate | Name of neutral gas evolved |
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Silver metal can displace hydrogen gas from nitric acid.
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When a candle burns, both physical and chemical changes take place.
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| Column I | Column II | ||
| 1. | Burning of coal | a. | Rusting |
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Write a note on the catalyst.
Write a note on the following:
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