Advertisements
Advertisements
प्रश्न
Give reason for the following:
Molybdenum is used in the manufacture of ammonia.
उत्तर
Molybdenum increases the efficiency of the catalyst iron used in the manufacture of ammonia.
APPEARS IN
संबंधित प्रश्न
How would you show that setting of curd is a chemical change?
Give reason .
A person suffering from acidity is advised to take an antacid.
FILL IN THE BLANK
A .............. change is a temporary change.
FILL IN THE BLANK
Negatively charged ions are called ..........
Fill in the blank
A new substance is always formed in a _______ change.
Fill in the blank
A change in which the substance can be brought back to its original state is called a _______ change.
Name the type of chemical reaction shown by the following equation:
CaCO3 → CaO + CO2
Complete the statement by filling the gaps using appropriate term from the terms given in the bracket.
(slow, coloured, arrow, fast, smell, milky, physical, product, chemical, reactant, covalent, ionic, octet, duplet, exchange, sharing, equality sign)
Chlorine (Cl2) molecule is formed by ______ of electrons between two chlorine atoms.
Match the pairs.
| a. | Photosynthesis | i. | Tendency to lose electrons |
| b. | Water | ii. | Reactant in combustion process |
| c. | Sodium chloride | iii. | Chemical change |
| d. | Dissolution of salt in water | iv. | Covalent bond |
| e. | Carbon | v. | Ionic bond |
| f. | Fluorine | vi. | Physical change |
| g. | Magnesium | vii. | Tendency to form anion |
Give reason for the following:
Blue solution of copper sulphate changes to green when a piece of iron is added to this solution.
Give reason for the following:
Colourless concentrated sulphuric acid in a test tube changes to blue on adding a small piece of copper to it.
What do you observe when H2S is passed through a lead nitrate solution.
What do you observe when Cobalt chloride paper is introduced in water vapour.
Give a chemical test to distinguish between the following gases.
SO2 and Cl2
Distinguish by heating the following in dry test tubs.
Ammonium Chloride and iodine.
Give examples of exothermic reactions i.e. heat evolved in each of the following:
(a) reaction between a solid and a liquid
(b) reaction between two gases
Give two examples of exothermic reactions seen in everyday life.
What happens when cane sugar is strongly heated? Mention any two changes in it.
Give two examples for each of the following cases:
Chemical changes.
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.
Write a word equation for the chemical change, if any.
Assertion (A): Cutting paper into very small pieces is an irreversible change.
Reason (R): Physical changes are always reversible.
