CBSE 2025 · Region 3 · Set 1 · Q21 · 2 marks
List the possible sources of energy required in decomposition reactions. Illustrate any one with a suitable example.What is observed when hydrated ferrous sulphate crystals are heated in a dry boiling tube ? Give balanced chemical equation(s) of the reactions(s) that occur(s).
List the possible sources of energy required in decomposition reactions. Illustrate any one with a suitable example.
What is observed when hydrated ferrous sulphate crystals are heated in a dry boiling tube ? Give balanced chemical equation(s) of the reactions(s) that occur(s).
Marking-scheme solution
Heat, light, electricity
\[2 \mathrm{AgBr}(\mathrm{~s}) \xrightarrow{\text { Sunlight }} 2 \mathrm{Ag}(\mathrm{~s})+\mathrm{Br}_{2}(\mathrm{~g})
\]
Observation:
Water droplets on upper part of the test tube/Colour changes from green to white/White to brown on heating strongly/Pungent smell of burning Sulphur.
\[\begin{aligned}
& \mathrm{Fe} \mathrm{SO}_{4.7 \mathrm{H}_{2} \mathrm{O}} \rightarrow \mathrm{FeSO}_{4}+7 \mathrm{H}_{2} \mathrm{O} \\
& 2 \mathrm{FeSO}_{4} \xrightarrow{\text { Heat }} \mathrm{Fe}_{2} \mathrm{O}_{3}+\mathrm{SO}_{3}+\mathrm{SO}_{2}
\end{aligned}
\]
Chemical Reactions and EquationsCombination and Decomposition ReactionsUnderstandvery_short_answermedium
More from Chemical Reactions and Equations
- Why do we balance a chemical equation? Name and state the law that suggests the balancing of a chemical…2025 · asked 3×
- The main observations while performing the experiment of burning magnesium ribbon in air are: (i) Magnesium…2025 · asked 3×
- In which one of the following situations a chemical reaction does not occur?2025 · asked 3×
- The colour of the solution observed after about 1 hour of placing iron nails in copper sulphate solution is2025 · asked 3×
- Assertion: Silver chloride turns grey in sunlight. Reason (R): Decomposition of silver chloride into silver…2025 · asked 3×
- Assertion: Decomposition reactions are generally endothermic reactions. Reason (R): Decomposition of organic…2025 · asked 3×
- Electrolysis of water is a decomposition reaction. The mass ratio (M H: M O) of hydrogen and oxygen gases…2025 · asked 3×
- The values of a, b, c and d in the following balanced chemical equation are respectively: a Pb(NO 3) 2 heat b…2025 · asked 3×
CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.