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प्रश्न
State the various characteristics of chemical reactions.
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उत्तर
- Evolution of gas: Zinc and dilute sulphuric acid react to form zinc sulphate with the evolution of hydrogen gas.
- Formation of precipitate: Sulphuric acid and barium chloride react to form white precipitates of barium sulphate.
- Change in colour: The purple colour of the potassium permanganate solution, upon the addition of citric acid, changes to a colourless solution.
- Change in temperature: Barium hydroxide and ammonium chloride react to form barium chloride, ammonia and water. This is an endothermic reaction in which heat is absorbed, causing the temperature to fall.
- Change in state: Combustion of candle wax (solid) leads to the formation of water (liquid) and carbon dioxide (gas).
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