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Chemical Changes and Reactions — CHEMISTRY STD 9 — Question

ICSE BoardEnglish MediumSTD 9CHEMISTRYChemical Changes and Reactions3 Marks
Question
Decomposition reactions can occur by heat.
Give two balanced reactions for each.
✓

Answer

Heat:
In these types of reactions, a single reactant breaks down to give simpler products. For example, when ferrous sulfate crystals are heated, they lose water and the colour of the crystals changes. This is because ferrous sulfate decomposes to ferric oxide, sulfur dioxide and sulfur trioxide.
$\underset{\text { (Ferrous sulphate) }}{2 \mathrm{FeSO}_4(\mathrm{~s})} \xrightarrow{\Delta} \underset{\text { Ferric oxide }}{\mathrm{Fe}_2 \mathrm{O}_3(\mathrm{~s})}+\mathrm{SO}_2(\mathrm{~g})+\mathrm{SO}_3(\mathrm{~g})$
Thermal decomposition of calcium carbonate to produce calcium oxide and Carbon dioxide is very important in many industries. The product calcium oxide, which is also called lime or quicklime, is used to manufacture cement.
$\underset{\text { (Lime stone) }}{\left.\mathrm{CaCO}_3(\mathrm{~s})\right)} \xrightarrow{\Delta} \underset{\text { (Quick lime) }}{\mathrm{CaO}(\mathrm{s})}+\mathrm{CO}_2(\mathrm{~g})$

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