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प्रश्न
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 – Thermal decomposition of mercury [II] oxide.
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उत्तर
Thermal decomposition of mercury [II] oxides: Red colour of Hg[II]0 changes to silvery (Hg metal).
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संबंधित प्रश्न
Complete and balance the following chemical equations
NaCI + `AgNO_3` `→`
Fill in the blank
A catalyst either ................or ............... the rate of a chemical change but itself remains ............... at the end of the reaction.
FILL IN THE BLANK
On reaction with sulphuric acid solution, barium chloride forms a white precipitate of ........ sulphate.
How is precipitate formation in a chemical reaction indicated?
State what you would observe when the following substance is heated in a glass test tube Copper (II) carbonate Red lead .
Give reason for the following:
Silver nitrate solution is kept in coloured bottles.
What do you understand by precipitation reaction? Explain with examples.
State the type of reactions for the following represent and balance the ones that are not balanced.
NaOH + HCl → NaCl + H2O
Name: Two carbonates do not produce carbon dioxide on heating.
State the original colour of the following substance and colour of residue obtained after heating.
Lead nitrate
Select the correct answer for the following options:
The pale blue precipitated obtained when copper [II] sulphate reacts with sodium hydroxide.
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 water to quicklime.
Give balanced equation for the following conversion affected by heat alone on the substance:
Copper carbonate to copper oxide
Complete the table given below.
| Heat on sodium chloride | Colour imparted to flame during flame test |
Select the correct answer from the options given below:
State the gaseous product formed, when
An active metal reacts with dilute sulphuric acid.
The chemical change is ______.
Silver metal can displace hydrogen gas from nitric acid.
Match the following:
| 1. | Sodium Chloride | a. | CaSO41/2H2O |
| 2. | Calcium sulphate dihydrate | b. | C2H5Oh |
| 3. | Magnesium sulphate hydrate | c. | CaSO4.2H2O |
| 4. | Calcium sulphate hemihydrate | d. | NaCl |
| 5. | Phenol | e. | MgSO4.H2O |
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.
Do you think formation of rust from iron is a chemical change?
Photosynthesis is a chemical charge. Justify your answer.
