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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
What are (i) positive catalysts and (ii) negative catalysts? Support your answer with one example for each of them.
Complete and balance the following chemical equations:
Fe `"SO"_4` + NaOH `→`
(aq.) (aq.)
Write the missing reactants and products and balance the equations.
NaOH + ............... `→` NaCI + ...................
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer.
Reduction is a chemical reaction in which there is
- removal of hydrogen
- removal of oxygen
- addition of oxygen
- none of these
TRUE \ FALSE
The evolution of a gas during a chemical reaction is shown by an arrow pointing downwards. True or false ?
A solution of a substance ‘X’ is used for white washing write the reaction of the substance ‘X’ named in (a) above with water.
When electric current is passed through acidulated water ______ of water takes place.
Complete and balance the following reaction:
NaCl(aq) + AgNO3(aq) →
Name: A brown gas
What is observed in performing the following :
| Hydrogen | Oxygen | Carbon dioxide | Chlorine | |
| Litmus test | ||||
| Apply a burning splint to the gas | ||||
| Colour of gas | colourless | colourless | colourless | greenish-yellow |
| Odour of gas |
What do you observe when H2S is passed through a lead nitrate solution.
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.
Give balanced equation for the following conversion affected by heat alone on the substance:
Copper nitrate to nitrogen dioxide
Give a suitable example with an equation to show the representation of a chemical reaction.
Name the solid residual product formed reaction and state its colour during – thermal decomposition of the following substance.
Ammonium dichromate.
Name the solid residual product formed reaction and state its colour during – thermal decomposition of the following substance.
Calcium hydroxide.
The chemical change is ______.
Silver articles turning black: ______:: Boiling of H2O: physical 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.
Photosynthesis is a chemical charge. Justify your answer.
