\(\Delta H_{\text {reaction }}=\Sigma(\mathrm{B.E})_{\text {reactant }}-\Sigma(\mathrm{B.E})_{\text {product }}\)
\(=\left[(\mathrm{B.E})_{\mathrm{H}-\mathrm{H}}+(\mathrm{B.E})_{\mathrm{Cl}-\mathrm{Cl}}\right]-\left[2 \mathrm{B.E}_{(\mathrm{H}-\mathrm{Cl})}\right]\)
\(=434+242-(431) \times 2\)
\(\Delta H_{\text {reaction }}=-186 \mathrm{kJ}\)
Heat of formation is the amount of heat absorbed or evolved when one mole of substance is directly obtained from its constituent element.
Hence, enthalpy of formation of \(\mathrm{HCl}=-186 / 2\; \mathrm{kJ}\)
\(=-93 \;\mathrm{kJ} \mathrm{mol}^{-1}\)
$(i)\,\,{C_{12}}{H_{22}}{O_{11}}\,\, + \,\,12{O_2}\,\, \to \,\,12\,\,C{O_2}\, + \,\,11{H_2}O,\,\,\,\,\,\,\,\,\,\,\,\,\Delta H\,\, = \,\, - 5200.7\,kJ\,mo{l^{ - 1}} $
$(ii)\,\,C\,\, + \,\,{O_2}\, \to \,\,C{O_2},\,\,\,\,\,\,\,\,\,\,\,\,\Delta H\,\, = \,\, - \,394.5\,\,kJ\,\,mo{l^{ - 1}}$
$(iii)\,\,{H_2}\,\, + \,\frac{1}{2}{O_2}\,\, \to \,\,\,{H_2}O,\,\,\,\,\,\,\,\,\,\Delta H\,\, = \,\, - \,285.8\,kJ\,\,mo{l^{ - 1}}$
$A$. પ્રવાહીનું બાષ્પમાં બાષ્પીભવન થાય છે.
$B$. સ્ફટિકમય ધનનું તાપમાન $130 \mathrm{~K}$ માંથી $0 \mathrm{~K}$ નીચું (ધટાડવામાં આવે છે) લઈ જવામાં આવે છે.
$C$. $2 \mathrm{NaHCO}_{3(\mathrm{~s})} \rightarrow \mathrm{Na}_2 \mathrm{CO}_{3(\mathrm{~s})}+\mathrm{CO}_{2(\mathrm{~g})}+\mathrm{H}_2 \mathrm{O}_{(\mathrm{g})}$
$D$. $\mathrm{Cl}_{2(\mathrm{~g})} \rightarrow 2 \mathrm{Cl}_{(\mathrm{g})}$
નીચે આપેલા વિકલ્પોમાંથી સાચો જવાબ શોધો.