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प्रश्न
State the various characteristics of chemical reactions.
उत्तर
Following are the various characteristics of a chemical reaction:
- 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: Purple colour of potassium permanganate solution on addition of citric acid changes to 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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संबंधित प्रश्न
Write complete balanced equation for the following reaction:
Sulphur dioxide (gas) + Oxgyen (gas) 
Sulphur trioxide (gas)
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C + CO2 → CO
When hydrogen is passed over copper oxide, copper and steam are formed. Write a balanced equation for this reaction and state which of the chemicals are non-metals.
Is Electrolysis of water an endothermic reaction or an exothermic reaction?
Balance the equation stepwise.
Ag(s) + HCl(aq) → AgCl ↓+ H2 ↑
What is the limitation of the reaction given in question 2?
Balance the following equation:
Fe + H2O → Fe3O4 + H2
Balance the following simple equation:
CaO + HCl → CaCl2 + H2O
What are reactants? Explain with the help of example.
Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is(are) correct?
- In beakers A and B, exothermic process has occurred.
- In beakers A and B, endothermic process has occurred.
- In beaker C exothermic process has occurred.
- In beaker C endothermic process has occurred.
