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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 – Addition of dilute acid to an active metal.
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उत्तर
Addition of dil. acid to an active metal: Gas is evolved, test tube or flask becomes hot (heat is produced).
APPEARS IN
संबंधित प्रश्न
Complete and balance the following chemical equations:
Ba`"CI"_2` + `"H"_2"SO"_4` `→`
(aq.) (aq.)
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer
Which of the following is a reducing agent?
- oxygen
- chlorine
- hydrogen
- none of these
Fill in the blank
A new substance is always formed in a _______ change.
Fill in the blank:
In some chemical reactions an insoluble ________ is formed when two solutions are mixed.
Write true or false :
When potassium iodide solution is added to lead acetate solution a red precipitate is formed.
Choose the correct option from the bracket and explain the statement giving a reason.
(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, decomposition)
Addition of an aqueous solution of ZnSO4 to an aqueous solution of BaCl2 is an example of ______ reaction.
What do you understand by precipitation reaction? Explain with examples.
Give an example of the following chemical changes.
A reaction where colour change is noticed.
Name: A greenish-yellow gas.
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.
A chemical reaction is often accompanied by external indications or characteristics.
Burning of paper is a ______ change.
The changes in which new substance with new chemical properties are formed are ______.
Chemical change is a temporary change.
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 |
Iron benches kept in lawns and gardens get____________. It is a _________ change because a new _________ is formed.
Write word equations for two chemical reactions with the help of materials given in the box.
| Air, copper sulphate, iron, vinegar, iron oxide, carbon dioxide, iron sulphate, copper, lime water, water |
A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.
Are these changes chemical in nature?
Write the effects of chemical reactions.
Collect information about the types of fuels used for cooking in your area. Discuss with your teachers/parents/others which fuels are less polluting and why.
