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Question
Explain the following type of chemical reaction, giving two examples for it:
Decomposition reaction
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Solution
A reaction in which a compound breaks up due to heat application into two or more simple substances is called a decomposition reaction.
\[\ce{AB->[heat] A + B}\]
Examples:
- Mercuric oxide when heated, decomposes to form two elements mercury and oxygen
\[\ce{2HgO_{(s)}->[heat] 2Hg_{(s)} + O2_{(g)}}\] - CaCO3 when heated decomposes to calcium oxide and carbon dioxide.
\[\ce{CaCO3 ->[heat] CaO + CO2}\]
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RELATED QUESTIONS
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?
Give one example of a decomposition reaction which is carried out with electricity.
What type of chemical reaction is represented by the following equation?
X → Y + Z
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?
Answer the following question.
2 g of silver chloride is taken in a china dish and the china dish is placed in sunlight for some time. What will be your observation in this case? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction.
What is electrolysis?
The following reaction is used for the preparation of oxygen gas in the laboratory:
\[\ce{2KClO3_{(s)} ->[Heat] 2KCl + 3O2_{(g)}}\]
Which of the following statement about the reaction is correct?
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Assertion: Silver bromide decomposition is used in black and white photography.
Reason: Light provides energy for this exothermic reaction.
