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Questions
What is a decomposition reaction?
What is meant by decomposition reaction?
Solution 1
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.
Solution 2
The reaction in which there is only one reactant giving rise to two or more products is called a decomposition reaction.
RELATED QUESTIONS
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?
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Taking into consideration the relationship in the first pair, complete the second pair
2H2 + O2 → 2H2O :Combination Reaction :: 2HgO → 2Hg + O2:_________
Rewrite the following statements by selecting the correct options:
\[\ce{CaCO3 ->[\Delta] CaO + CO2 ^}\] is a __________ reaction.
State an important use of decomposition reactions.
Give one example of a decomposition reaction which is carried out by applying heat.
What type of reaction is represented by the following equation?
NH4 CI → NH3 + HCI
What type of chemical reaction take place when lime-stone is heated?
What type of chemical reaction take place when electricity is passed through water?
What type of chemical reaction is represented by the following equation?
X → Y + Z
Name the product formed on strongly heating ferrous sulphate crystals. What type of chemical reaction occurs in this change?
State the change in colour observed in following case mentioning the reason:
Silver chloride is exposed to sunlight.
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 :
A student wants to study a decomposition reaction by taking ferrous sulphate crystals. Write two precautions he must observe while performing the experiment.
How can the rate of the chemical reaction, namely, decomposition of hydrogen peroxide be increased?
Classify the following reaction into different type:
\[\ce{2KClO3(s)->[\Delta] 2KCl(aq) + 3O2(g)}\]
Differentiate between direct combination reaction and a decomposition reaction.
Give a balanced equation for –
An electrolytic decomposition reaction involving a neutral liquid
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.
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:
Assertion: Decomposition of vegetable matter into compost is an endothermic reaction.
Reason: Decomposition reaction involves breakdown of a single reactant into simpler products.
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?
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.
These consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
Assertion: Silver bromide decomposition is used in black and white photography.
Reason: Light provides energy for this exothermic reaction.
Complete the following reaction:
\[\ce{C_12H_22O11->[Heat]}\] ______ + ______.
A metal nitrate 'A' on heating gives a metal oxide along with evolution of a brown coloured gas 'B' and a colourless gas, which helps in burning. Aqueous solution of 'A' when reacted with potassium iodide forms a yellow precipitate.
- Identify 'A' and 'B'
- Name the types of the reactions involved in the above statement.
What is observed when silver chloride is exposed to sunlight? Give the type of reaction involved.
Write one equation for decomposition reactions where energy is supplied in the form of light.
Write one equation for decomposition reactions where energy is supplied in the form of electricity.
A solution of a substance ‘X’ is used for whitewashing.
- Name the substance ‘X’ and write its formula.
- Write the reaction of the substance ‘X’ named in the above formula with water.
