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Hydrogen — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryHydrogen5 Marks
Question
Saline hydrides are known to react with water violently producing fire. $\mathrm{Can} \mathrm{~CO}_2$, a well known fire extinguisher, be used in this case? Explain.
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Answer

Saline hydrides (i.e., NaH, LiH, etc.) react with water to form a base and hydrogen gas. The chemical equation used to represent the reaction can be written as,
$\mathrm{MH}_{\mathrm{s}}+\mathrm{H}_2 \mathrm{O}_{\mathrm{eq}} \longrightarrow \mathrm{MOH}_{\mathrm{eq}}+\mathrm{H}_{2(\mathrm{~g})}$
The reaction is violent and produces fire. $\mathrm{CO}_2$ is heavier than dioxygen. It is used as a fire extinguisher because it covers the fire as a blanket and inhibits the supply of dioxygen, thereby dousing the fire. $\mathrm{CO}_2$ can be used in the present case as well. It is heavier than dihydrogen and will be effective in isolating the burning surface from dihydrogen and dioxygen.

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