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प्रश्न
State the various characteristics of chemical reactions.
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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
Translate the following statement into chemical equation and then balance it.
Hydrogen sulphide gas burns in the air to give water and sulphur dioxide.
Giving examples, state the difference between balanced and unbalanced chemical equations.
Aluminium burns in chlorine to form aluminium chloride (AlCl3). Write a balanced chemical equation for this reaction.
What is meant by chemical reaction? Explain with the help of an example.
When a mixture of gases X and Y is compressed to 300 atm pressure and then passed over a catalyst consisting of a mixture of zinc oxide and chromium oxide (heated to a temperature of 300°C), then an organic compounds Z having the molecular formula CH4O is formed. X is a highly poisonous gas which is formed in appreciable amounts when a fuel burns in a limited supply of air; Y is a gas which can be made by the action of a dilute acid on an active metal; and Z is a liquid organic compound which can react with sodium metal to produce hydrogen gas.
(a) What are X, Y and Z?
(b) Write a balanced chemical equation of the reaction which takes place when X and Y combine to form Z. Indicate the conditions under which the reaction occurs.
Balance the following equation. Also name the product formed.
K2O + H2O → KOH
Balance the equation stepwise.
SO2(g) + H2S(aq) → S(s) + H2O(l)
Balance the following equation:
PbO + NH3 → Pb + H2O + N2
Write the balanced chemical equation of the following reaction.
potassium bicarbonate + sulphuric acid → potassium sulphate + carbon dioxide + water
Answer the following question.
What is observed when 2 mL of dilute hydrochloric acid is added to 1 g of sodium carbonate taken in a clean and dry test tube? Write a chemical equation for the reaction involved.
Write word equation for the following molecular equation:
\[\ce{CaCO3 + 2HCl ->[\triangle] CaCl2 + H2O + CO2 [g]}\]
Word equation:
State which characteristic does [g] in the above reaction indicate. The word equation of:
In certain reaction a change of state is observed i.e. solid to liquid, liquid to gas etc. – State the change of state of the products – to give the respective reactant.
NH3 + HCl ⇌ NH4Cl
In certain reaction an insoluble solid called precipitate is formed. State the colour and name of the precipitate formed in the following reaction involving addition of:
Copper [II] sulphate to sodium hydroxide.
Balance the following simple equation:
NaHCO3 + H2SO4 → Na2SO4 + H2O + CO2
CaCO3 + 2HCl[dil.] → CaCl2 + H2O + CO2 [g]
State the information provided by the above chemical equation.
CaCO3 + 2HCl[dil.] → CaCl2 + H2O + CO2 [g]
State the information not conveyed by the above chemical equation.
Write a balanced equation for the following word equation:
Calcium hydroxide + Ammonium chloride → Calcium chloride + Water + Ammonia
Why should a magnesium ribbon be cleaned before burning in air?
