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प्रश्न
Give examples of exothermic reactions i.e. heat evolved in each of the following:
(a) reaction between a solid and a liquid
(b) reaction between two gases
Give two examples of exothermic reactions seen in everyday life.
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उत्तर
(a) Reaction between a solid and a liquid:
CaO + H2O → Ca(OH)3 + Δ
(b) Reaction between two gases are:
\[\ce{N2 + 3H2 ⇌[Fe-450°][200 atoms.] 2NH3 + \triangle}\]
[finely divided iron (Fe) - catalyst]
Examples of exothermic reactions are:
- Rusting of iron – the reaction is slow and the heat evolved is very less, hence unnoticeable.
- Setting of cement – cement setting liberates heat, hence concrete structures are set slowly.
- Human Body – many chemical reactions in our body are exothermic & provide energy to survive.
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संबंधित प्रश्न
State whether the following statement is true or false. In case a statement is false, write the corrected statement.
Iron pipes coated with zinc do not get rusted easily.
Write the missing reactants and products and balance the equations.
................+ HCI `→` NaCI + `"H"_2"O"` + .........................
What do you observe when :
an iron nail is kept in tap water for few days
What is the reaction called when oxidation and reduction take place simultaneously? Explain with one example.
Explain by writing a word equation.
Respiration is a chemical change.
Explain by writing a word equation.
Bubbles are seen on adding lemon juice to baking soda.
Name the gases which turn moist red litmus blue.
Name: Gas with rotten egg smell.
Distinguish by heating the following in dry test tubs.
Copper Sulphate and copper carbonate
Write your observation and a balanced equation in the case of the following substances being heated.
Ammonium chloride
Give a word equation for the following reaction.
Two solids which combine on heating, to give a liquid.
What is the role of a catalyst in a chemical reaction?
Discuss how acid rain occurs due to emission of smoke from vehicles and industries?
Silver metal can displace hydrogen gas from nitric acid.
Rusting of Iron: undesirable change:: Dead plants turn into manure: ______.
Iron benches kept in lawns and gardens get____________. It is a _________ change because a new _________ is formed.
Iron and rust are the same substances.
Match the following:
| Column I | Column II | ||
| 1. | Burning of coal | a. | Rusting |
| 2. | Painting of a surface | b. | Evaporation |
| 3. | Dipping iron in the water | c. | Chemical change |
| 4. | Salt from seawater | d. | Prevention of rusting |
______ is the chemical name of rust.
Define the following term:
Chemical change
