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प्रश्न
What is a chemical reaction?
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उत्तर
“Chemical reaction is a chemical change in which matter changes into a new substance or substances.”
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संबंधित प्रश्न
Define precipitation reaction.
Fill in the blank.
Melting of ice is a _______ change.
Write true or false :
When iron and sulphur are heated together a grey mass is formed which is attracted by a magnet .
A solution of a substance ‘X’ is used for white washing write the reaction of the substance ‘X’ named in (a) above with water.
Choose the correct option from the bracket and explain the statement giving reason.
(Oxidation, displacement, electrolysis, reduction, zinc, copper, double displacement, decomposition)
To prevent rusting, a layer of ______ metal is applied on iron sheets.
Define an electrochemical reaction.
Give reason for the following:
Silver nitrate solution is kept in coloured bottles.
State the main characteristics of chemical reactions. Give at least one example in each case.
Name the gases which turn moist red litmus blue.
Give a word equation for the following reaction.
A compound which on heating shows – colour change from brown to yellow.
Give balanced equation for the following conversion affected by heat alone on the substance:
Copper nitrate to nitrogen dioxide
Give balanced equation for the following conversion affected by heat alone on the substance:
Zinc nitrate to nitrogen dioxide
Give a balanced equation for a reaction involving the evolution of gas on the addition of dilute acid to sodium sulphite.
Circle the odd one out. Give reason for your choice
Burning of paper is a ______ change.
Arrange the following statements in correct sequence:
- One side is water-loving and other water-hating molecules.
- When you agitate the cloth, the dirt is surrounded by many molecules and taken away from the cloth.
- The dirt surrounded by the detergent molecules floats in the water making it dirty.
- Finally, the cloth is clean.
- The detergent molecules have two sides.
- Water hating goes and joins with dirt and oil in the cloth while the water-loving joins with the water molecules.
Which of the following are chemical changes?
(i) Decaying of wood
(ii) Burning of wood
(iii) Sawing of wood
(iv) Hammering of a nail into a piece of wood
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 a note on the following:
Fermentation
What is thermochemical reactions?
