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If enthalpy of combustion of carbon to $\mathrm{CO}_2(\mathrm{~g})$ is $-394.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$, the enthalpy change for the formation of $17.6 \mathrm{~g}$ of $\mathrm{CO}_2$ from carbon and dioxygen at the same temperature in $\mathrm{kJ}$ is
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Verified Answer
The correct answer is:
-157.6
Reaction for combusion is
$$
\mathrm{C}+\mathrm{O}_2 \longrightarrow \mathrm{CO}_2, \Delta \mathrm{H}=-394 \mathrm{~kJ} \mathrm{~mol}^{-1}
$$
$\because$ Molar mass of $\mathrm{CO}_2=12+(2 \times 10)$
and
$$
=44 \mathrm{~g}
$$
$\because 44 \mathrm{~g}$ of formation of $\mathrm{CO}_2$ gives heat $=-394.0 \mathrm{~kJ}$
$\therefore 17.6 \mathrm{~g}$ of formation of
$$
\mathrm{CO}_2 \text {, gives heat }=\frac{-394 \times 17.6}{44}=-157.6 \mathrm{~kJ} \text {. }
$$
$$
\mathrm{C}+\mathrm{O}_2 \longrightarrow \mathrm{CO}_2, \Delta \mathrm{H}=-394 \mathrm{~kJ} \mathrm{~mol}^{-1}
$$
$\because$ Molar mass of $\mathrm{CO}_2=12+(2 \times 10)$
and
$$
=44 \mathrm{~g}
$$
$\because 44 \mathrm{~g}$ of formation of $\mathrm{CO}_2$ gives heat $=-394.0 \mathrm{~kJ}$
$\therefore 17.6 \mathrm{~g}$ of formation of
$$
\mathrm{CO}_2 \text {, gives heat }=\frac{-394 \times 17.6}{44}=-157.6 \mathrm{~kJ} \text {. }
$$
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