JEE Mains · Chemistry · STD 11 - 5. Thermodynamics and thermochemistry
Given :
\(\begin{aligned}
& \Delta \mathrm{H}_{\text {sub }}^{\ominus}[\mathrm{C}(\text { graphite })]=710 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
& \Delta_{\mathrm{C}-\mathrm{H}} \mathrm{H}^{\ominus}=414 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
& \Delta_{\mathrm{H}-\mathrm{H}} \mathrm{H}^{\Theta}=436 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
& \Delta_{\mathrm{C}=\mathrm{C}} \mathrm{H}^{\Theta}=611 \mathrm{~kJ} \mathrm{~mol}^{-1}
\end{aligned}\)
The \(\Delta \mathrm{H}_{\mathrm{f}}^{\ominus}\) for \(\mathrm{CH}_2=\mathrm{CH}_2\) is _____ \(\mathrm{kJ} \mathrm{mol}^{-1}\) (nearest integer value)
- A 30
- B 35
- C 20
- D 25
Answer & Solution
Correct Answer
(D) 25
Step-by-step Solution
Detailed explanation
\(\left[\Delta H _{ f }^{ o }\right]_{ C _2 H _{(4)}}=2 \times\left[\Delta H _{ sub }^{ o }\right]_{ C _{( s )}}+2 \times \Delta H _{ H - H }^{ o }\) \(-1 \times \Delta H _{ C = C }^{ o }-4 \times \Delta H _{ CH }^{ o }\)…
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