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प्रश्न
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
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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:
\[\ce{2H2(g) + O2(g) -> 2H2O(l)}\]
\[\ce{NH3(g) + HCl(g) -> NH4Cl(s)}\]
APPEARS IN
संबंधित प्रश्न
What does one mean by exothermic reaction? Give example.
Write one equation for decomposition reactions where energy is supplied in the form of heat.
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 following equation?
\[\ce{CaCO3 -> CaCO + CO2}\]
A metal salt MX when exposed to light splits up to form metal M and a gas X2. Metal M is used in making ornaments whereas gas X2 is used in making bleaching powder. The salt MX is itself used in black and white photography.
(a) What do you think metal M is?
(b) What could be gas X2?
(c) Name the metal salt MX.
(d) Name any two salt solutions which on mixing together can produce a precipitate of salt MX.
(e) What type of chemical reaction takes place when salt MX is exposed to light? Write the equation of the reaction?
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer.
Thermal decomposition of a substance is brought about with the help of
- reactants
- water
- wind
- heat
Identify the type of following reaction :
Differentiate between direct combination reaction and a decomposition reaction.
Give a balanced equation for the following type of reaction:
A thermal decomposition reaction in which a metallic nitrate decomposes to give – a basic oxide.
Differentiate between the following:
Thermal decomposition and thermal dissociation.
Differentiate between the following:
Electrolytic decomposition and photochemical decomposition.
Which of the following is an endothermic process?
Marble statues are corroded or stained rain water. Identify the main reason.
Balance the following chemical equation and identify the type of chemical reaction.
`"H"_2"O"_2("l") overset("U V")(->) "H"_2"O"("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
- Write a balanced chemical equation of the reaction.
- Identify the brown gas X evolved.
- Identify the type of reaction.
- What could be the pH range of aqueous solution of the gas X?
When lead nitrate is heated strongly in a boiling tube, two gases are liberated and a solid residue is left behind in the test tube.
- Name the type of chemical reaction and define it.
- Write the name and formula of the coloured gas liberated.
- Write the balanced chemical equation for the reaction.
- Name the residue left in the test tube and state the method of testing its nature (acidic/basic).
