Question

What happens when Calcium carbonate is heated? Silver bromide is exposed to sunlight? Lead is added to copper chloride solution? Write balanced chemical equations of the reactions involved in support of your answer.

Hint:

Heating → Thermal decomposition. Sunlight → Photochemical reaction. Reactive metal → Displacement reaction.

Answer 1

(1) When Calcium Carbonate is Heated:

When calcium carbonate (CaCO₃) is heated strongly, it undergoes a thermal decomposition reaction. In this process, calcium carbonate breaks down into calcium oxide and carbon dioxide gas.

Calcium oxide (CaO) is commonly known as quicklime, and carbon dioxide (CO₂) is released as a gas.

Balanced Chemical Equation:
CaCO₃(s) → CaO(s) + CO₂(g)

This reaction is an example of a decomposition reaction because a single compound splits into two simpler substances upon heating.

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(2) When Silver Bromide is Exposed to Sunlight:

Silver bromide (AgBr) undergoes a photochemical decomposition reaction when exposed to sunlight. It decomposes into silver metal and bromine gas.

This reaction is the basis of black and white photography, as the greyish silver metal formed creates the image.

Balanced Chemical Equation:
2AgBr(s) → 2Ag(s) + Br₂(g)

This reaction is called a photochemical reaction because it takes place in the presence of light.

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(3) When Lead is Added to Copper Chloride Solution:

When lead (Pb) is added to copper chloride (CuCl₂) solution, a displacement reaction takes place. Lead is more reactive than copper, so it displaces copper from the solution.

As a result, lead chloride (PbCl₂) and copper metal are formed.

Balanced Chemical Equation:
Pb(s) + CuCl₂(aq) → PbCl₂(s) + Cu(s)

This is an example of a single displacement reaction because one element replaces another element from its compound.

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Conclusion:
– Heating calcium carbonate results in thermal decomposition.
– Silver bromide decomposes in sunlight through a photochemical reaction.
– Lead displaces copper from copper chloride solution in a displacement reaction.