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प्रश्न
What is meant by a chemical reaction? Explain with the help of an example.
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उत्तर
A chemical reaction is the process in which atoms of some elements rearrange, that is, undergo a chemical change, to form a new product with different properties. This involves breaking old bonds between the reacting atoms and making new chemical bonds between the rearranged atoms.
For example, the burning of magnesium ribbon in air. In this reaction, magnesium ribbon, on heating, combines with oxygen to form a white powder of magnesium oxide, which has properties entirely different from those of magnesium and oxygen.
\[\ce{2Mg_{(s)} + O2_{(g)} ->[heat] 2MgO_{(s)}}\]
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संबंधित प्रश्न
Why should a magnesium ribbon be cleaned before it is burnt in the air?
On what basis is a chemical equation balanced?
State whether the following statement is true or false:
A chemical equation can be balanced easily by altering the formula of a reactant or product.
Giving examples, state the difference between balanced and unbalanced chemical equations.
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:
- elements
- compounds
- reactants
- products
- metal
- non-metal
The chemical reaction between quicklime and water is characterised by:
(a) evolution of hydrogen gas
(b) formation of slaked lime precipitate
(c) change in temperature of mixture
(d) change in colour of the product
The metal M reacts vigorously with water to form a solution S and a gas G. The solution S turns red litmus to blue whereas gas G, which is lighter than air, burns with a pop sound. Metal M has a low melting point and it is used as a coolant in nuclear reactors.
(a) What is metal M?
(b) What is solution S? Is it acidic or alkaline?
(c) What is gas G?
(d) Write a balanced chemical equation for the reaction which takes place when metal M reacts with water.
(e) Is this reaction exothermic or endothermic?
Balance the following equation. Also name the product formed.
`"Zn" + "HCI" → "ZnCI" _2 + "H"_2`
Write the chemical equation for the following word equation and balance them.
Carbon + Oxygen → Carbon dioxide
Balance the following equation:
\[\ce{S + HNO3 -> H2SO4 + NO2 + H2O}\]
Choose the correct answer from the options given below.
The formula of sodium carbonate is Na2CO3 and that of calcium hydrogen carbonate is
Write the balanced chemical equation of the following reaction.
aluminium sulphate + sodium hydroxide → sodium sulphate + sodium meta aluminate + water.
\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]
0.02 moles of pure MnO2 is heated strongly with conc. HCl. Calculate the mass of acid required.
Identify the type of reaction taking place of the following case and write the balanced chemical equation of the reaction:
Zinc reacts with silver nitrate to produce zinc nitrate and silver.
Give one example in the case where supplying energy [given below] is necessary for a chemical reaction.
Catalyst
Write a balanced equation for the following word equation:
Lead dioxide [lead (IV) oxide] → Lead monoxide + Oxygen
Write a balanced equation for the following word equation:
Aluminium + Oxygen → Aluminium oxide
Give a balanced equation by the partial equation method, [steps are given below].
Oxidation of Lead [II] Sulphide by Ozone
- Ozone first decomposes to give molecular oxygen & nascent oxygen.
- Nascent oxygen then oxidises lead [II] sulphide to lead [II] sulphate.
What are reactants? Explain with the help of example.
What is called thermolysis reactions?
