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प्रश्न
How do the following help in bringing about a chemical change?
heat.
उत्तर
Some chemical reactions take place only in the presence of heat.
e.g. When lead nitrate is heated, it breaks into lead monoxide, nitrogen dioxide and oxygen.
\[\ce{\underset{\text{(lead nitrate)}}{2Pb(NO3)2}->[heat]\underset{\text{lead monoxide}}{2PbO} +\underset{\text{nitrogen dioxide}}{4NO2} + O2}\]
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संबंधित प्रश्न
Give one example that illustrates the following characteristics of a chemical reaction:
Change in state
How do the following help in bringing about a chemical change?
pressure.
Fill in the blank
A catalyst either ................or ............... the rate of a chemical change but itself remains ............... at the end of the reaction.
Define precipitation.
FILL IN THE BLANK
The new substances formed during a chemical reaction are called the ..................
TRUE \ FALSE
Evaporation of water is a physical change. True or false ?
What are chemical reactions?
What do you observe when :
an iron nail is kept in tap water for few days
| Reactants | Products | Type of chemical reaction |
| BaCl2(aq) + ZnSO4(aq) | H2CO3(aq) | Displacement |
| 2AgCl(s) | FeSO4(aq) + Cu(s) | Combination |
| CuSO4(aq) + Fe(s) | BaSO4↓ + ZnCl2(aq) | Decomposition |
| H2O(l) + CO2(g) | 2Ag(s) + Cl2(g) | Double displacement |
Show with the help of diagram of electronic configuration how the following compound is formed from the constituent atoms.
Water
Show with the help of diagram of electronic configuration how the following compound is formed from the constituent atoms.
Hydrogen chloride
Define the following terms
Precipitate
Define Electrochemical reaction
Give an example
Write the chemical reaction where the following changes are observed.
Colour change is noticed
What is a chemical change? Give two examples of chemical change?
Define:
Photochemical reaction
Give one example
Complete the following table and write your observations.
|
Hydrogen sulphide |
Ammonia |
Sulphur dioxide |
Hydrogen chloride |
|
|
Shake the gas with red litmus solution |
||||
|
Shake the gas with blue litmus solution |
||||
|
Apply a burning splint to a gas |
What is observed in performing the following :
| Hydrogen | Oxygen | Carbon dioxide | Chlorine | |
| Litmus test | ||||
| Apply a burning splint to the gas | ||||
| Colour of gas | colourless | colourless | colourless | greenish-yellow |
| Odour of gas |
Give a chemical test to distinguish between the following gases.
H2 and CO2
Write your observation and a balanced equation in the case of the following substances being heated.
Zinc carbonate.
Complete the table given below.
| Addition of dil. H2SO4 to zinc | Test for gas evolved |
Give a suitable example with an equation to show the representation of a chemical reaction.
What happens when cane sugar is strongly heated? Mention any two changes in it.
______ gas causes tears in our eyes while cutting onions.
Higher order Thinking question
Peeled and unpeeled banana does not look the same. Does that mean peeling banana is a chemical change?
Write some materials prepared by chemical changes.
Iron benches kept in lawns and gardens get____________. It is a _________ change because a new _________ is formed.
______ occurs in the absence of air and in the presence of micro-organisms such as yeast.
Magnesium + oxygen → magnesium oxide.
2Mg + O2 → 2Mg O
