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प्रश्न
What is meant by a decomposition reaction?
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उत्तर
A decomposition reaction is a chemical reaction in which a single compound breaks down to simpler products. It is the opposite of a combination reaction.
संबंधित प्रश्न
Why is the amount of gas collected in one of the test tubes in the following Activity double of the amount collected in the other? Name this gas.
- Take a plastic mug. Drill two holes at its base and fit rubber stoppers in these holes. Insert carbon electrodes in these rubber stoppers as shown in the following Fig.
- Connect these electrodes to a 6 volt battery.
- Fill the mug with water such that the electrodes are immersed. Add a few drops of dilute sulphuric acid to the water.
- Take two test tubes filled with water and invert them over the two carbon electrodes.
- Switch on the current and leave the apparatus undisturbed for some time.
- You will observe the formation of bubbles at both the electrodes. These bubbles displace water in the test tubes.
- Is the volume of the gas collected the same in both the test tubes?
• Once the test tubes are filled with the respective gases, remove them carefully. - Test these gases one by one by bringing a burning candle close to the mouth of the test tubes.
Caution: This step must be performed carefully by the teacher.
- What happens in each case?
- Which gas is present in each test tube?
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.
- What is compound A?
- What is compound B?
- What is gas C?
- What do you think is the black substance X? What is its function?
- What is the general name of substances like X?
What type of reaction is represented by the digestion of food in our body?
Give one example of a decomposition reaction which is carried out by applying heat.
Give one example of a decomposition reaction which is carried out with electricity.
What type of chemical reaction is used to extract metals from their naturally occurring compounds like oxides or chlorides?
What type of reaction is represented by the following equation?
\[\ce{CaCO3 -> CaO + CO2}\]
What type of reaction is represented by the following equation?
\[\ce{2FeSO4 -> Fe2O3 + SO2 + SO3}\]
What type of reaction is represented by the following equation?
\[\ce{NH4NO2 -> N2 + 2H2O}\]
State the change in colour observed in the following case, mentioning the reason:
Silver chloride is exposed to sunlight.
When a green iron salt is heated strongly, its colour finally changes to brown and odour of burning sulphur is given out.
- Name the iron salt.
- Name the type of reaction that takes place during the heating of iron salt.
- Write a chemical equation for the reaction involved.
MULTIPLE CHOICE QUESTIONS
Tick the most appropriate answer.
Thermal decomposition of a substance is brought about with the help of
- reactants
- water
- wind
- heat
What is a redox reaction? Explain with an example.
What does one mean by endothermic reaction? Give example.
Give a scientific reason.
When the gas formed on heating limestone is passed through freshly prepared lime water, the lime water turns milky.
Study the following figure and answer questions.
a) After heating Calcium carbonate, which gas is formed in a test tube?
b) When we pass this gas through limewater what change, did you observe?
c) Write down the chemical reaction showing the product formation after heating the Calcium carbonate.
(a) Design an activity to demonstrate the decomposition reaction of lead nitrate.
(b) Draw labelled diagram of the experimental set-up. List two main observations.
(c) Write balanced chemical equation for the reaction stating the physical state of the reactant and the products.
A student wants to study a decomposition reaction by taking ferrous sulphate crystals. Write two precautions he must observe while performing the experiment.
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.
Classify the following reaction into –
- Direct combination
- Decomposition
- Displacement
- Double decomposition
The reaction is – Zinc hydroxide on heating gives zinc oxide and water.
Give a balanced equation for –
A thermal decomposition reaction involving heat on limestone [calcium carbonate]
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:
Thermal decomposition and thermal dissociation.
Differentiate between the following:
Electrolytic decomposition and photochemical decomposition.
Explain the reaction given in the figure.
Photolysis is a decomposition reaction caused by ______
Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is:
Which one of the following processes involves chemical reactions?
Give the ratio in which hydrogen and oxygen are present in water by volume.
Marble statues are corroded or stained rain water. Identify the main reason.
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?
The reaction of calcium carbonate, with freshly prepared lime water, is shown below:
Answer the questions with the help of a diagram:
- What type of reaction does calcium carbonate undergoes?
- What change in colour is observed in lime?
- Write the chemical equation.
Write the molecular formula of calcium carbonate.
Write one equation for the decomposition reaction where energy is supplied in the form of light.
