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The gases hydrogen and chlorine donot re...

The gases hydrogen and chlorine donot react with each other even if kept together for a long time. However, in the presence of sun light, they readily combine. What does actually happen ?

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We know that in chemical reactions, energy is needed to break the bonds present in the reacting molecules so that they may combine to form the products. In the present case, sun light is the source of energy in the form of photons. The energy made available helps in breaking the bonds present in the reactant molecules and the chemical reaction leading to hydrogen chloride gas takes place.
`H_(2)(g) + Cl_(2)(g) overset("sunlight")to 2HCl(g)`
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