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प्रश्न
What do you observe when :
an iron nail is kept in tap water for few days
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उत्तर
We observe reddish brown coating on the nail called rust (entirely new substance) is chemical change.
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संबंधित प्रश्न
What are (i) positive catalysts and (ii) negative catalysts? Support your answer with one example for each of them.
TRUE \ FALSE
The evolution of a gas during a chemical reaction is shown by an arrow pointing downwards. True or false ?
Fill in the blank
A change in which the substance can be brought back to its original state is called a _______ change.
What is the reaction called when oxidation and reduction take place simultaneously? Explain with one example.
Match the column in the following table.
| 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.
Sodium chloride
Define the following term:
Precipitate
Complete the following table and write your observations.
|
Hydrogen sulphide |
Ammonia |
Sulphur dioxide |
Hydrogen chloride |
|
|
Shake the gas with red litmus solution |
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Shake the gas with blue litmus solution |
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Apply a burning splint to a gas |
What do you observe when HCI is passed through a silver nitrate solution.
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 hydrochloric acid to silver nitrate.
State the following reaction represent oxidation or reduction.
\[\ce{Cl- ->Cl}\]
State the following reaction represent oxidation or reduction.
\[\ce{Al->Al+++}\]
State whether the following reaction is oxidation or reduction.
\[\ce{Na->Na+}\]
Silver metal can displace hydrogen gas from nitric acid.
The changes in which new substance with new chemical properties are formed are ______.
What is the use of indicator?
Classify the following processes into physical or chemical changes:
- Beating of aluminium metal to make aluminium foil.
- Digestion of food.
- Cutting of a log of wood into pieces.
- Burning of crackers.
How would you show that the settling of curd is a chemical change?
What is thermochemical reactions?
