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Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions. - Science

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प्रश्न

Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

संक्षेप में उत्तर

उत्तर

Decomposition reactions occur when a compound breaks up into two or more simpler substances. On the other hand, combination reactions occur when two or more substances combine to form a single substance.

Thus, decomposition reactions are the opposite of combination reactions.

Decomposition Reactions:

\[\ce{CaCO3(s) -> CaO(s) + CO2(g)}\]

\[\ce{2H2O(l) ->[Electricity] 2H2(g) + O2(g)}\]

Combination Reactions:

\[\ce{2H2(g) + O2(g) -> 2H2O(l)}\]

\[\ce{NH3(g) + HCl(g) -> NH4Cl(s)}\]

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अध्याय 1: Chemical Reactions and Equations - Exercise 2 [पृष्ठ ४७]

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लखमीर सिंग Chemistry (Science) [English] Class 10
अध्याय 1 Chemical Reactions and Equations
Exercise 2 | Q 37.1 | पृष्ठ ४७
एनसीईआरटी Science [English] Class 10
अध्याय 1 Chemical Reactions and Equations
Exercises | Q 11 | पृष्ठ १५

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संबंधित प्रश्न

Write one equation for decomposition reactions where energy is supplied in the form of heat.


Decomposition reactions require energy either in the form of heat or light or electricity for breaking down the reactants. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light and electricity


The white solid compound A decomposes quite rapidly on heating in the presence of a black substance X to form a solid compound B and a gas C. When an aqueous solution of compound B is reacted with silver nitrate solution, then a white precipitate of silver chloride is obtained along with potassium nitrate solution. Gas C does not burn itself but helps burn other things.
(a) What is compound A?
(b) What is compound B?
(c) What is gas C?
(d) What do you think is the black substance X? What is its function?
(e) What is the general name of substances like X?


What type of reaction is represented by the digestion of food in our body?


State an important use of decomposition reactions.


What type of chemical reaction take place when lime-stone is heated?


When a green iron salt is heated strongly, its colour finally changes to brown and odour of burning sulphur is given out.
(a) Name the iron salt.
(b) Name the type of reaction that takes place during the heating of iron salt.
(c) Write a chemical equation for the reaction involved.


How will you obtain  Nitrogen dioxide from lead nitrate.
Also give balanced equations for the reactions


Classify the following reaction into – 

  1. Direct combination 
  2. Decomposition
  3. Displacement
  4. Double decomposition

The reaction is – Zinc hydroxide on heating gives zinc oxide and water.


Give a balanced equation for –

A double decomposition neutralization reaction involving an acid and a base


Give a balanced equation for –

A white precipitate obtained during a double decomposition reaction involving a silver salt with sodium salt.


Complete the statement by filling in the blank with the correct word:

Decomposition of silver salts in the presence of sunlight is an example of _________.


Differentiate between the following:

Electrolytic decomposition and photochemical decomposition.


Chemical volcano is an example of ______ type of reaction.


Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is:


Balance the following chemical equation and identify the type of chemical reaction.

`"HgO"("s") overset("(heat)")(->) "Hg"("l") + "O"_2("g")`


On heating blue coloured powder of copper (II) nitrate, in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed

  1. Write a balanced chemical equation of the reaction.
  2. Identify the brown gas X evolved.
  3.  Identify the type of reaction.
  4. What could be the pH range of aqueous solution of the gas X?

The reaction of calcium carbonate, with freshly prepared lime water, is shown below:

Answer the questions with the help of a diagram:

  1. What type of reaction does calcium carbonate undergoes?
  2. What change in colour is observed in lime?
  3. Write the chemical equation.


Write the molecular formula of calcium carbonate.


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